20661560172 has 72 divisors (see below), whose sum is σ = 58365517392. Its totient is φ = 6108364800.

The previous prime is 20661560167. The next prime is 20661560177. The reversal of 20661560172 is 27106516602.

It is a happy number.

20661560172 is a `hidden beast` number, since 20 + 6 + 6 + 1 + 560 + 1 + 72 = 666.

It is an interprime number because it is at equal distance from previous prime (20661560167) and next prime (20661560177).

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

It is not an unprimeable number, because it can be changed into a prime (20661560177) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 620053 + ... + 652524.

It is an arithmetic number, because the mean of its divisors is an integer number (810632186).

Almost surely, 2^20661560172 is an apocalyptic number.

20661560172 is a gapful number since it is divisible by the number (22) formed by its first and last digit.

It is an amenable number.

20661560172 is an abundant number, since it is smaller than the sum of its proper divisors (37703957220).

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

20661560172 is a wasteful number, since it uses less digits than its factorization.

20661560172 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1272639 (or 1272634 counting only the distinct ones).

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

The spelling of 20661560172 in words is "twenty billion, six hundred sixty-one million, five hundred sixty thousand, one hundred seventy-two".