20640915720 has 384 divisors, whose sum is σ = 71752262400. Its totient is φ = 5334211584.

The previous prime is 20640915709. The next prime is 20640915751. The reversal of 20640915720 is 2751904602.

20640915720 is a `hidden beast` number, since 2 + 0 + 640 + 9 + 1 + 5 + 7 + 2 + 0 = 666.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is an unprimeable number.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 53061286 + ... + 53061674.

It is an arithmetic number, because the mean of its divisors is an integer number (186854850).

Almost surely, 2^20640915720 is an apocalyptic number.

20640915720 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 20640915720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (35876131200).

20640915720 is an abundant number, since it is smaller than the sum of its proper divisors (51111346680).

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

20640915720 is a wasteful number, since it uses less digits than its factorization.

20640915720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 571 (or 555 counting only the distinct ones).

The product of its (nonzero) digits is 30240, while the sum is 36.

The spelling of 20640915720 in words is "twenty billion, six hundred forty million, nine hundred fifteen thousand, seven hundred twenty".