20979840 has 192 divisors, whose sum is σ = 78140160. Its totient is φ = 4773888.

The previous prime is 20979809. The next prime is 20979877. The reversal of 20979840 is 4897902.

It is a tau number, because it is divible by the number of its divisors (192).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 93969 + ... + 94191.

It is an arithmetic number, because the mean of its divisors is an integer number (406980).

Almost surely, 2^20979840 is an apocalyptic number.

20979840 is a gapful number since it is divisible by the number (20) 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 20979840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (39070080).

20979840 is an abundant number, since it is smaller than the sum of its proper divisors (57160320).

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

20979840 is a wasteful number, since it uses less digits than its factorization.

20979840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 259 (or 240 counting only the distinct ones).

The product of its (nonzero) digits is 36288, while the sum is 39.

The square root of 20979840 is about 4580.3755304560. The cubic root of 20979840 is about 275.8041037980.

The spelling of 20979840 in words is "twenty million, nine hundred seventy-nine thousand, eight hundred forty".