20657487720 has 128 divisors (see below), whose sum is σ = 64824883200. Its totient is φ = 5256286464.

The previous prime is 20657487691. The next prime is 20657487757. The reversal of 20657487720 is 2778475602.

It is a self number, because there is not a number n which added to its sum of digits gives 20657487720.

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, 1147509 + ... + 1165371.

It is an arithmetic number, because the mean of its divisors is an integer number (506444400).

Almost surely, 2^20657487720 is an apocalyptic number.

20657487720 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 20657487720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32412441600).

20657487720 is an abundant number, since it is smaller than the sum of its proper divisors (44167395480).

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

20657487720 is a wasteful number, since it uses less digits than its factorization.

20657487720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 18319 (or 18315 counting only the distinct ones).

The product of its (nonzero) digits is 1317120, while the sum is 48.

The spelling of 20657487720 in words is "twenty billion, six hundred fifty-seven million, four hundred eighty-seven thousand, seven hundred twenty".