21712931 has 2 divisors, whose sum is σ = 21712932. Its totient is φ = 21712930.

The previous prime is 21712907. The next prime is 21712939. The reversal of 21712931 is 13921712.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21712931 - 2¹⁴ = 21696547 is a prime.

It is a super-2 number, since 2×21712931² = 942902745221522, which contains 22 as substring.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21712931.

It is not a weakly prime, because it can be changed into another prime (21712939) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10856465 + 10856466.

It is an arithmetic number, because the mean of its divisors is an integer number (10856466).

Almost surely, 2^21712931 is an apocalyptic number.

21712931 is a deficient number, since it is larger than the sum of its proper divisors (1).

21712931 is an equidigital number, since it uses as much as digits as its factorization.

21712931 is an evil number, because the sum of its binary digits is even.

The product of its digits is 756, while the sum is 26.

The square root of 21712931 is about 4659.7136178096. The cubic root of 21712931 is about 278.9798377879.

The spelling of 21712931 in words is "twenty-one million, seven hundred twelve thousand, nine hundred thirty-one".