1237

1237 is a prime number.

1237 has a representation as a sum of two squares: 1237 = 9² + 37².

1237 is the hypotenuse of a primitive Pythagorean triple: 1237² = 612² + 1275².

1237² - (1237 - 5)² = 12345.

1237 is also a prime number when its digits are reversed (emirp): 7321. It is the smallest 4-digit emirp with distinct digits. The sum of its digits, 1 + 2 + 3 + 7 = 13, is equal to the smallest double-digit emirp. 1237 is an emirp formed from the number 12 and the 12th prime; its reversal (7321) is formed from the 21st prime and the number 21.

1237 Geneviève is an asteroid discovered in 1931.

Source: Prime Curios!