21356979 has 16 divisors (see below), whose sum is σ = 32938752. Its totient is φ = 12055968.

The previous prime is 21356971. The next prime is 21356983. The reversal of 21356979 is 97965312.

It is not a de Polignac number, because 21356979 - 2³ = 21356971 is a prime.

It is a super-2 number, since 2×21356979² = 912241104012882, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21356979.

It is not an unprimeable number, because it can be changed into a prime (21356971) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 4384 + ... + 7869.

It is an arithmetic number, because the mean of its divisors is an integer number (2058672).

Almost surely, 2^21356979 is an apocalyptic number.

21356979 is a deficient number, since it is larger than the sum of its proper divisors (11581773).

21356979 is a wasteful number, since it uses less digits than its factorization.

21356979 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12346.

The product of its digits is 102060, while the sum is 42.

The square root of 21356979 is about 4621.3611631207. The cubic root of 21356979 is about 277.4469405899.

The spelling of 21356979 in words is "twenty-one million, three hundred fifty-six thousand, nine hundred seventy-nine".