21908879 has 4 divisors (see below), whose sum is σ = 22048584. Its totient is φ = 21769176.

The previous prime is 21908851. The next prime is 21908899. The reversal of 21908879 is 97880912.

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 21908879 - 2¹⁶ = 21843343 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 (21908839) 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, 69617 + ... + 69930.

It is an arithmetic number, because the mean of its divisors is an integer number (5512146).

Almost surely, 2^21908879 is an apocalyptic number.

21908879 is a deficient number, since it is larger than the sum of its proper divisors (139705).

21908879 is a wasteful number, since it uses less digits than its factorization.

21908879 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 139704.

The product of its (nonzero) digits is 72576, while the sum is 44.

The square root of 21908879 is about 4680.6921496719. The cubic root of 21908879 is about 279.8165422385.

The spelling of 21908879 in words is "twenty-one million, nine hundred eight thousand, eight hundred seventy-nine".