21156975 has 108 divisors (see below), whose sum is σ = 46860840. Its totient is φ = 9072000.

The previous prime is 21156953. The next prime is 21157039. The reversal of 21156975 is 57965112.

21156975 is a `hidden beast` number, since 21 + 1 + 569 + 75 = 666.

It is not a de Polignac number, because 21156975 - 2⁷ = 21156847 is a prime.

Its product of digits (18900) is a multiple of the sum of its prime divisors (135).

It is a congruent number.

It is an unprimeable number.

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 107 ways as a sum of consecutive naturals, for example, 209425 + ... + 209525.

Almost surely, 2^21156975 is an apocalyptic number.

21156975 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

21156975 is an abundant number, since it is smaller than the sum of its proper divisors (25703865).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21156975 is a wasteful number, since it uses less digits than its factorization.

21156975 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 150 (or 135 counting only the distinct ones).

The product of its digits is 18900, while the sum is 36.

The square root of 21156975 is about 4599.6711839000. The cubic root of 21156975 is about 276.5781438053.

The spelling of 21156975 in words is "twenty-one million, one hundred fifty-six thousand, nine hundred seventy-five".