21978860 has 24 divisors (see below), whose sum is σ = 46316256. Its totient is φ = 8760960.

The previous prime is 21978799. The next prime is 21978871. The reversal of 21978860 is 6887912.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 4505 + ... + 8015.

It is an arithmetic number, because the mean of its divisors is an integer number (1929844).

Almost surely, 2^21978860 is an apocalyptic number.

21978860 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21978860 is an abundant number, since it is smaller than the sum of its proper divisors (24337396).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21978860 is a wasteful number, since it uses less digits than its factorization.

21978860 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3833 (or 3831 counting only the distinct ones).

The product of its (nonzero) digits is 48384, while the sum is 41.

The square root of 21978860 is about 4688.1616866316. The cubic root of 21978860 is about 280.1141541341.

The spelling of 21978860 in words is "twenty-one million, nine hundred seventy-eight thousand, eight hundred sixty".