21621879 has 6 divisors (see below), whose sum is σ = 31231616. Its totient is φ = 14414580.

The previous prime is 21621871. The next prime is 21621881. The reversal of 21621879 is 97812612.

21621879 is a `hidden beast` number, since 21 + 621 + 8 + 7 + 9 = 666.

It is not a de Polignac number, because 21621879 - 2³ = 21621871 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21621871) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1201207 + ... + 1201224.

Almost surely, 2^21621879 is an apocalyptic number.

21621879 is a deficient number, since it is larger than the sum of its proper divisors (9609737).

21621879 is a wasteful number, since it uses less digits than its factorization.

21621879 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2402437 (or 2402434 counting only the distinct ones).

The product of its digits is 12096, while the sum is 36.

The square root of 21621879 is about 4649.9332253270. The cubic root of 21621879 is about 278.5893291399.

It can be divided in two parts, 21621 and 879, that added together give a square (22500 = 150²).

The spelling of 21621879 in words is "twenty-one million, six hundred twenty-one thousand, eight hundred seventy-nine".