665156720 has 20 divisors (see below), whose sum is σ = 1546489560. Its totient is φ = 266062656.

The previous prime is 665156707. The next prime is 665156741. The reversal of 665156720 is 27651566.

It is a tau number, because it is divible by the number of its divisors (20).

It is a super-3 number, since 3×665156720³ (a number of 27 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4157150 + ... + 4157309.

It is an arithmetic number, because the mean of its divisors is an integer number (77324478).

Almost surely, 2^665156720 is an apocalyptic number.

It is an amenable number.

665156720 is an abundant number, since it is smaller than the sum of its proper divisors (881332840).

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

665156720 is a wasteful number, since it uses less digits than its factorization.

665156720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8314472 (or 8314466 counting only the distinct ones).

The product of its (nonzero) digits is 75600, while the sum is 38.

The square root of 665156720 is about 25790.6324079112. The cubic root of 665156720 is about 872.9204362259.

The spelling of 665156720 in words is "six hundred sixty-five million, one hundred fifty-six thousand, seven hundred twenty".