21156291 has 48 divisors (see below), whose sum is σ = 35875840. Its totient is φ = 11897280.

The previous prime is 21156277. The next prime is 21156307. The reversal of 21156291 is 19265112.

21156291 is a `hidden beast` number, since 2 + 11 + 562 + 91 = 666.

It is not a de Polignac number, because 21156291 - 2⁶ = 21156227 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21156241) 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 47 ways as a sum of consecutive naturals, for example, 68760 + ... + 69066.

Almost surely, 2^21156291 is an apocalyptic number.

21156291 is a deficient number, since it is larger than the sum of its proper divisors (14719549).

21156291 is a wasteful number, since it uses less digits than its factorization.

21156291 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 376 (or 373 counting only the distinct ones).

The product of its digits is 1080, while the sum is 27.

The square root of 21156291 is about 4599.5968301581. The cubic root of 21156291 is about 276.5751632045.

The spelling of 21156291 in words is "twenty-one million, one hundred fifty-six thousand, two hundred ninety-one".