21391256 has 16 divisors (see below), whose sum is σ = 40203240. Its totient is φ = 10670400.

The previous prime is 21391213. The next prime is 21391259. The reversal of 21391256 is 65219312.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21391259) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 731 + ... + 6581.

Almost surely, 2^21391256 is an apocalyptic number.

It is an amenable number.

21391256 is a deficient number, since it is larger than the sum of its proper divisors (18811984).

21391256 is a wasteful number, since it uses less digits than its factorization.

21391256 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6314 (or 6310 counting only the distinct ones).

The product of its digits is 3240, while the sum is 29.

The square root of 21391256 is about 4625.0682157131. The cubic root of 21391256 is about 277.5952912466.

The spelling of 21391256 in words is "twenty-one million, three hundred ninety-one thousand, two hundred fifty-six".