401

401 is a prime number.

401 is the start of the first occurrence of three consecutive primes using no prime digits: 401, 409, 419.

401 is the sum of seven consecutive primes: 401 = 43 + 47 + 53 + 59 + 61 + 67 + 71. It is also the sum of nine consecutive primes: 401 = 29 + 31 + 37 + 41 + 43 + 47 + 53 + 59 + 61.

401 is a divisor of 20⁴ - 1.

401 has a representation as a sum of two squares: 401 = 1² + 20².

401 is the hypotenuse of a primitive Pythagorean triple: 401² = 40² + 399².

401 was the hull number of the RMS Titanic.

Source: Number Gossip