21372778 has 16 divisors (see below), whose sum is σ = 36717120. Its totient is φ = 9140256.

The previous prime is 21372761. The next prime is 21372787. The reversal of 21372778 is 87727312.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 6625 + ... + 9307.

It is an arithmetic number, because the mean of its divisors is an integer number (2294820).

Almost surely, 2^21372778 is an apocalyptic number.

21372778 is a deficient number, since it is larger than the sum of its proper divisors (15344342).

21372778 is a wasteful number, since it uses less digits than its factorization.

21372778 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3261.

The product of its digits is 32928, while the sum is 37.

The square root of 21372778 is about 4623.0701919828. The cubic root of 21372778 is about 277.5153382751.

The spelling of 21372778 in words is "twenty-one million, three hundred seventy-two thousand, seven hundred seventy-eight".