21620651 has 24 divisors (see below), whose sum is σ = 26115264. Its totient is φ = 17729280.

The previous prime is 21620603. The next prime is 21620659. The reversal of 21620651 is 15602612.

It is not a de Polignac number, because 21620651 - 2¹⁴ = 21604267 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21620659) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 79646 + ... + 79916.

It is an arithmetic number, because the mean of its divisors is an integer number (1088136).

Almost surely, 2^21620651 is an apocalyptic number.

21620651 is a deficient number, since it is larger than the sum of its proper divisors (4494613).

21620651 is a wasteful number, since it uses less digits than its factorization.

21620651 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 339 (or 320 counting only the distinct ones).

The product of its (nonzero) digits is 720, while the sum is 23.

The square root of 21620651 is about 4649.8011785452. The cubic root of 21620651 is about 278.5840549426.

The spelling of 21620651 in words is "twenty-one million, six hundred twenty thousand, six hundred fifty-one".