21022978 has 16 divisors (see below), whose sum is σ = 32138496. Its totient is φ = 10311840.

The previous prime is 21022921. The next prime is 21022997. The reversal of 21022978 is 87922012.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 45175 + ... + 45637.

It is an arithmetic number, because the mean of its divisors is an integer number (2008656).

Almost surely, 2^21022978 is an apocalyptic number.

21022978 is a deficient number, since it is larger than the sum of its proper divisors (11115518).

21022978 is a wasteful number, since it uses less digits than its factorization.

21022978 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 849.

The product of its (nonzero) digits is 4032, while the sum is 31.

The square root of 21022978 is about 4585.0821148590. The cubic root of 21022978 is about 275.9930072442.

The spelling of 21022978 in words is "twenty-one million, twenty-two thousand, nine hundred seventy-eight".