21879131 has 4 divisors (see below), whose sum is σ = 22387992. Its totient is φ = 21370272.

The previous prime is 21879103. The next prime is 21879139. The reversal of 21879131 is 13197812.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21879131 - 2¹⁴ = 21862747 is a prime.

It is a super-2 number, since 2×21879131² = 957392746630322, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21879139) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 254366 + ... + 254451.

It is an arithmetic number, because the mean of its divisors is an integer number (5596998).

Almost surely, 2^21879131 is an apocalyptic number.

21879131 is a deficient number, since it is larger than the sum of its proper divisors (508861).

21879131 is an equidigital number, since it uses as much as digits as its factorization.

21879131 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 508860.

The product of its digits is 3024, while the sum is 32.

The square root of 21879131 is about 4677.5133350959. The cubic root of 21879131 is about 279.6898393800.

The spelling of 21879131 in words is "twenty-one million, eight hundred seventy-nine thousand, one hundred thirty-one".