665756720 has 80 divisors (see below), whose sum is σ = 1643921568. Its totient is φ = 249876480.

The previous prime is 665756699. The next prime is 665756747. The reversal of 665756720 is 27657566.

It is a tau number, because it is divible by the number of its divisors (80).

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 667262 + ... + 668258.

Almost surely, 2^665756720 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 665756720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (821960784).

665756720 is an abundant number, since it is smaller than the sum of its proper divisors (978164848).

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

665756720 is a wasteful number, since it uses less digits than its factorization.

665756720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1518 (or 1512 counting only the distinct ones).

The product of its (nonzero) digits is 529200, while the sum is 44.

The square root of 665756720 is about 25802.2619163514. The cubic root of 665756720 is about 873.1828279513.

The spelling of 665756720 in words is "six hundred sixty-five million, seven hundred fifty-six thousand, seven hundred twenty".