20979864 has 128 divisors (see below), whose sum is σ = 62899200. Its totient is φ = 6462720.

The previous prime is 20979809. The next prime is 20979877. The reversal of 20979864 is 46897902.

It is a happy number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 203637 + ... + 203739.

It is an arithmetic number, because the mean of its divisors is an integer number (491400).

Almost surely, 2^20979864 is an apocalyptic number.

20979864 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 20979864, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31449600).

20979864 is an abundant number, since it is smaller than the sum of its proper divisors (41919336).

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

20979864 is a wasteful number, since it uses less digits than its factorization.

20979864 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 182 (or 172 counting only the distinct ones).

The product of its (nonzero) digits is 217728, while the sum is 45.

The square root of 20979864 is about 4580.3781503278. The cubic root of 20979864 is about 275.8042089672.

The spelling of 20979864 in words is "twenty million, nine hundred seventy-nine thousand, eight hundred sixty-four".