21879117 has 24 divisors (see below), whose sum is σ = 34871928. Its totient is φ = 13132800.

The previous prime is 21879103. The next prime is 21879139. The reversal of 21879117 is 71197812.

It can be written as a sum of positive squares in 4 ways, for example, as 617796 + 21261321 = 786^2 + 4611^2 .

It is not a de Polignac number, because 21879117 - 2⁴ = 21879101 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21879167) 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, 2517 + ... + 7077.

It is an arithmetic number, because the mean of its divisors is an integer number (1452997).

Almost surely, 2^21879117 is an apocalyptic number.

It is an amenable number.

21879117 is a deficient number, since it is larger than the sum of its proper divisors (12992811).

21879117 is a wasteful number, since it uses less digits than its factorization.

21879117 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4621 (or 4618 counting only the distinct ones).

The product of its digits is 7056, while the sum is 36.

The square root of 21879117 is about 4677.5118385740. The cubic root of 21879117 is about 279.6897797240.

The spelling of 21879117 in words is "twenty-one million, eight hundred seventy-nine thousand, one hundred seventeen".