21709431 has 16 divisors (see below), whose sum is σ = 32402400. Its totient is φ = 14364864.

The previous prime is 21709411. The next prime is 21709433. The reversal of 21709431 is 13490712.

It is not a de Polignac number, because 21709431 - 2⁵ = 21709399 is a prime.

It is a super-2 number, since 2×21709431² = 942598788687522, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a junction number, because it is equal to n+sod(n) for n = 21709395 and 21709404.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21709433) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 765 + ... + 6633.

It is an arithmetic number, because the mean of its divisors is an integer number (2025150).

Almost surely, 2^21709431 is an apocalyptic number.

21709431 is a deficient number, since it is larger than the sum of its proper divisors (10692969).

21709431 is a wasteful number, since it uses less digits than its factorization.

21709431 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6015 (or 6009 counting only the distinct ones).

The product of its (nonzero) digits is 1512, while the sum is 27.

The square root of 21709431 is about 4659.3380431130. The cubic root of 21709431 is about 278.9648469989.

The spelling of 21709431 in words is "twenty-one million, seven hundred nine thousand, four hundred thirty-one".