665505680 has 80 divisors (see below), whose sum is σ = 1816193280. Its totient is φ = 221999616.

The previous prime is 665505677. The next prime is 665505721. The reversal of 665505680 is 86505566.

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

It is a super-2 number, since 2×665505680² = 885795620224524800, which contains 22 as substring.

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, 4661 + ... + 36779.

It is an arithmetic number, because the mean of its divisors is an integer number (22702416).

Almost surely, 2^665505680 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 665505680, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (908096640).

665505680 is an abundant number, since it is smaller than the sum of its proper divisors (1150687600).

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

665505680 is a wasteful number, since it uses less digits than its factorization.

665505680 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 32176 (or 32170 counting only the distinct ones).

The product of its (nonzero) digits is 216000, while the sum is 41.

The square root of 665505680 is about 25797.3967678911. The cubic root of 665505680 is about 873.0730624427.

The spelling of 665505680 in words is "six hundred sixty-five million, five hundred five thousand, six hundred eighty".