21978010 has 16 divisors (see below), whose sum is σ = 40152096. Its totient is φ = 8659728.

The previous prime is 21978007. The next prime is 21978017. The reversal of 21978010 is 1087912.

It is a self number, because there is not a number n which added to its sum of digits gives 21978010.

It is not an unprimeable number, because it can be changed into a prime (21978017) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 15732 + ... + 17071.

It is an arithmetic number, because the mean of its divisors is an integer number (2509506).

Almost surely, 2^21978010 is an apocalyptic number.

21978010 is a deficient number, since it is larger than the sum of its proper divisors (18174086).

21978010 is a wasteful number, since it uses less digits than its factorization.

21978010 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 32877.

The product of its (nonzero) digits is 1008, while the sum is 28.

The square root of 21978010 is about 4688.0710318851. The cubic root of 21978010 is about 280.1105430869.

The spelling of 21978010 in words is "twenty-one million, nine hundred seventy-eight thousand, ten".