21878955 has 24 divisors (see below), whose sum is σ = 43341792. Its totient is φ = 10001664.

The previous prime is 21878939. The next prime is 21879019. The reversal of 21878955 is 55987812.

It is a happy number.

It is not a de Polignac number, because 21878955 - 2⁴ = 21878939 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a self number, because there is not a number n which added to its sum of digits gives 21878955.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 34414 + ... + 35043.

It is an arithmetic number, because the mean of its divisors is an integer number (1805908).

Almost surely, 2^21878955 is an apocalyptic number.

21878955 is a deficient number, since it is larger than the sum of its proper divisors (21462837).

21878955 is a wasteful number, since it uses less digits than its factorization.

21878955 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 69475 (or 69472 counting only the distinct ones).

The product of its digits is 201600, while the sum is 45.

The square root of 21878955 is about 4677.4945216430. The cubic root of 21878955 is about 279.6890894181.

The spelling of 21878955 in words is "twenty-one million, eight hundred seventy-eight thousand, nine hundred fifty-five".