23 (number)

23 (twenty-three) is the natural number following 22 and preceding 24.

In mathematics

Twenty-three is the ninth prime number, the smallest odd prime that is not a twin prime. Twenty-three is also the fifth factorial prime, the second Woodall prime. It is an Eisenstein prime with no imaginary part and real part of the form 3n − 1.

Twenty-three is the sum of three other, consecutive, prime numbers; 5, 7 and 11. It is the first prime number showing this characteristic.

The fifth Sophie Germain prime and the fourth safe prime, 23 is the next to last member of the first Cunningham chain of the first kind to have five terms (2, 5, 11, 23, 47). Since 14! + 1 is a multiple of 23 but 23 is not one more than a multiple 14, 23 is a Pillai prime. 23 is the smallest odd prime to be a highly cototient number, as the solution to x − φ(x) for the integers 95, 119, 143, 529.

Twenty-three is the aliquot sum of two integers; the discrete semiprimes 57 and 85 and is the base of the 23-aliquot tree.

23 is the first prime p for which unique factorization of cyclotomic integers based on the pth root of unity breaks down.

83rd Wallajahbad Light Infantry

The 83rd Wallajahbad Light Infantry were an infantry regiment in the British Indian Army. They could trace their origins to 1794, when they were raised as the 33rd Madras Battalion.

They took part in the Battle of Seringapatam during the Fourth Anglo-Mysore War and the Second Burmese War.

First World War

The regiment was stationed at Secunderabad in 1914 on the outbreak of war and was here until at least early 1916.

They sent a wing of the regiment as a draft to the 63rd Palamcottah L. I. in 1914, which saw action in East Africa until December 1916, when it rejoined the regiment at Mandalay.

Meanwhile the other wing was sent to serve in the Persian Gulf from 21 September 1916, being split up in detachments between Jask, Chabahar, Bandar Abbas, Henjam, Kishm Island, Lingeh and Bahrain, all port towns on the Gulf of Oman relieving the 94th Infantry detachments previously stationed there until they were relieved by the 3rd Brahmins from 16 July 1917.

They were joined by the other wing of the regiment and were sent to serve in Mesopotamia, where they were successively stationed at Basra, Tanoomah, and Nar Oomah from 24 July 1917 to 3 May 1919.

23rd (Northumbrian) Division

The 23rd (Northumbrian) Division was a motorised infantry division of the British Army that saw active service in World War II in France in 1940, later being disbanded. The division was raised in the Territorial Army as a 2nd Line duplicate of the 50th (Northumbrian) Infantry Division.

History

The 23rd (Northumbrian) Division was being raised on the outbreak of war and became operational in October 1939. It was sent to join the British Expeditionary Force in France on 22 April 1940 on labour and training duties, without any of its artillery, signals, or administration units. Two other divisions, the 12th (Eastern) and 46th Infantry Division, were sent to France in April in a similar state as the 23rd.

After the German breakthrough in May 1940, the partly trained division was ordered up to defend a frontage of 16 miles along the Canal du Nord. Outflanked, and faced with five German Panzer divisions, the infantry and engineers fell back towards Arras, doing what they could to hold up the enemy and suffering heavy casualties in the process. The division played a peripheral part in the Battle of Arras and by 27 May had retreated into the Dunkirk perimeter, by which time it was incapable of further action.