665978405625 has 405 divisors, whose sum is σ = 1396659706299. Its totient is φ = 317289960000.

The previous prime is 665978405611. The next prime is 665978405639. The reversal of 665978405625 is 526504879566.

It is a happy number.

The square root of 665978405625 is 816075.

It is a perfect power (a square), and thus also a powerful number.

665978405625 is a `hidden beast` number, since 6 + 65 + 9 + 7 + 8 + 4 + 0 + 562 + 5 = 666.

It is an interprime number because it is at equal distance from previous prime (665978405611) and next prime (665978405639).

It can be written as a sum of positive squares in 7 ways, for example, as 657806968809 + 8171436816 = 811053^2 + 90396^2 .

It is a tau number, because it is divible by the number of its divisors (405).

It is not a de Polignac number, because 665978405625 - 2⁷ = 665978405497 is a prime.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 404 ways as a sum of consecutive naturals, for example, 21483174360 + ... + 21483174390.

Almost surely, 2^665978405625 is an apocalyptic number.

665978405625 is a gapful number since it is divisible by the number (65) formed by its first and last digit.

665978405625 is the 816075-th square number.

665978405625 is the 408038-th centered octagonal number.

It is an amenable number.

665978405625 is an abundant number, since it is smaller than the sum of its proper divisors (730681300674).

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

665978405625 is an frugal number, since it uses more digits than its factorization.

665978405625 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 132 (or 52 counting only the distinct ones).

The product of its (nonzero) digits is 108864000, while the sum is 63.

The spelling of 665978405625 in words is "six hundred sixty-five billion, nine hundred seventy-eight million, four hundred five thousand, six hundred twenty-five".