21158931 has 16 divisors (see below), whose sum is σ = 30681504. Its totient is φ = 12916224.

The previous prime is 21158903. The next prime is 21158933. The reversal of 21158931 is 13985112.

It is not a de Polignac number, because 21158931 - 2⁵ = 21158899 is a prime.

It is a super-2 number, since 2×21158931² = 895400722125522, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21158933) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 3720 + ... + 7493.

It is an arithmetic number, because the mean of its divisors is an integer number (1917594).

Almost surely, 2^21158931 is an apocalyptic number.

21158931 is a deficient number, since it is larger than the sum of its proper divisors (9522573).

21158931 is a wasteful number, since it uses less digits than its factorization.

21158931 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11270.

The product of its digits is 2160, while the sum is 30.

The square root of 21158931 is about 4599.8838028802. The cubic root of 21158931 is about 276.5866669232.

The spelling of 21158931 in words is "twenty-one million, one hundred fifty-eight thousand, nine hundred thirty-one".