21978630 has 48 divisors (see below), whose sum is σ = 60156720. Its totient is φ = 5552064.

The previous prime is 21978617. The next prime is 21978631. The reversal of 21978630 is 3687912.

21978630 is a `hidden beast` number, since 2 + 19 + 7 + 8 + 630 = 666.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21978631) by changing a digit.

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 23 ways as a sum of consecutive naturals, for example, 4717 + ... + 8136.

It is an arithmetic number, because the mean of its divisors is an integer number (1253265).

Almost surely, 2^21978630 is an apocalyptic number.

21978630 is an abundant number, since it is smaller than the sum of its proper divisors (38178090).

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

21978630 is a wasteful number, since it uses less digits than its factorization.

21978630 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12885 (or 12882 counting only the distinct ones).

The product of its (nonzero) digits is 18144, while the sum is 36.

The square root of 21978630 is about 4688.1371566967. The cubic root of 21978630 is about 280.1131770364.

The spelling of 21978630 in words is "twenty-one million, nine hundred seventy-eight thousand, six hundred thirty".