21955978 has 16 divisors (see below), whose sum is σ = 36054720. Its totient is φ = 9944800.

The previous prime is 21955957. The next prime is 21955981. The reversal of 21955978 is 87955912.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 5238 + ... + 8446.

It is an arithmetic number, because the mean of its divisors is an integer number (2253420).

Almost surely, 2^21955978 is an apocalyptic number.

21955978 is a deficient number, since it is larger than the sum of its proper divisors (14098742).

21955978 is a wasteful number, since it uses less digits than its factorization.

21955978 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3533.

The product of its digits is 226800, while the sum is 46.

The square root of 21955978 is about 4685.7206489504. The cubic root of 21955978 is about 280.0169122438.

The spelling of 21955978 in words is "twenty-one million, nine hundred fifty-five thousand, nine hundred seventy-eight".