21753891 has 12 divisors (see below), whose sum is σ = 32272032. Its totient is φ = 14110416.

The previous prime is 21753887. The next prime is 21753911. The reversal of 21753891 is 19835712.

It is not a de Polignac number, because 21753891 - 2² = 21753887 is a prime.

It is a hoax number, since the sum of its digits (36) coincides with the sum of the digits of its distinct prime factors.

It is not an unprimeable number, because it can be changed into a prime (21753871) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 32331 + ... + 32996.

It is an arithmetic number, because the mean of its divisors is an integer number (2689336).

Almost surely, 2^21753891 is an apocalyptic number.

21753891 is a deficient number, since it is larger than the sum of its proper divisors (10518141).

21753891 is a wasteful number, since it uses less digits than its factorization.

21753891 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 65370 (or 65367 counting only the distinct ones).

The product of its digits is 15120, while the sum is 36.

The square root of 21753891 is about 4664.1066668763. The cubic root of 21753891 is about 279.1551532293.

The spelling of 21753891 in words is "twenty-one million, seven hundred fifty-three thousand, eight hundred ninety-one".