21642651 has 12 divisors (see below), whose sum is σ = 31455528. Its totient is φ = 14338944.

The previous prime is 21642637. The next prime is 21642667. The reversal of 21642651 is 15624612.

21642651 is a `hidden beast` number, since 2 + 1 + 6 + 4 + 2 + 651 = 666.

It is not a de Polignac number, because 21642651 - 2⁶ = 21642587 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21642601) 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, 5910 + ... + 8843.

It is an arithmetic number, because the mean of its divisors is an integer number (2621294).

Almost surely, 2^21642651 is an apocalyptic number.

21642651 is a deficient number, since it is larger than the sum of its proper divisors (9812877).

21642651 is a wasteful number, since it uses less digits than its factorization.

21642651 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 14922 (or 14919 counting only the distinct ones).

The product of its digits is 2880, while the sum is 27.

The square root of 21642651 is about 4652.1662695996. The cubic root of 21642651 is about 278.6785135782.

The spelling of 21642651 in words is "twenty-one million, six hundred forty-two thousand, six hundred fifty-one".