666655920 has 560 divisors, whose sum is σ = 2810391552. Its totient is φ = 143700480.

The previous prime is 666655919. The next prime is 666655931. The reversal of 666655920 is 29556666.

It is a tau number, because it is divible by the number of its divisors (560).

It is a Harshad number since it is a multiple of its sum of digits (45).

It is an unprimeable number.

It is a polite number, since it can be written in 111 ways as a sum of consecutive naturals, for example, 9389485 + ... + 9389555.

Almost surely, 2^666655920 is an apocalyptic number.

666655920 is a gapful number since it is divisible by the number (60) 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 666655920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1405195776).

666655920 is an abundant number, since it is smaller than the sum of its proper divisors (2143735632).

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

666655920 is a wasteful number, since it uses less digits than its factorization.

666655920 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 132 (or 111 counting only the distinct ones).

The product of its (nonzero) digits is 583200, while the sum is 45.

The square root of 666655920 is about 25819.6808655723. The cubic root of 666655920 is about 873.5757706720.

The spelling of 666655920 in words is "six hundred sixty-six million, six hundred fifty-five thousand, nine hundred twenty".