21913831 has 2 divisors, whose sum is σ = 21913832. Its totient is φ = 21913830.

The previous prime is 21913819. The next prime is 21913849. The reversal of 21913831 is 13831912.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21913831 - 2¹⁵ = 21881063 is a prime.

It is a super-2 number, since 2×21913831² = 960431978193122, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21913831.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21913861) 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 as a sum of consecutive naturals, namely, 10956915 + 10956916.

It is an arithmetic number, because the mean of its divisors is an integer number (10956916).

Almost surely, 2^21913831 is an apocalyptic number.

21913831 is a deficient number, since it is larger than the sum of its proper divisors (1).

21913831 is an equidigital number, since it uses as much as digits as its factorization.

21913831 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1296, while the sum is 28.

The square root of 21913831 is about 4681.2211013794. The cubic root of 21913831 is about 279.8376226893.

The spelling of 21913831 in words is "twenty-one million, nine hundred thirteen thousand, eight hundred thirty-one".