643966125625 has 15 divisors (see below), whose sum is σ = 804725140681. Its totient is φ = 515156851000.

The previous prime is 643966125613. The next prime is 643966125689. The reversal of 643966125625 is 526521669346.

The square root of 643966125625 is 802475.

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

It can be written as a sum of positive squares in 2 ways, for example, as 50486944249 + 593479181376 = 224693^2 + 770376^2 .

It is not a de Polignac number, because 643966125625 - 2⁹ = 643966125113 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 14 ways as a sum of consecutive naturals, for example, 20045826 + ... + 20077924.

Almost surely, 2^643966125625 is an apocalyptic number.

643966125625 is the 802475-th square number.

643966125625 is the 401238-th centered octagonal number.

It is an amenable number.

643966125625 is a deficient number, since it is larger than the sum of its proper divisors (160759015056).

643966125625 is an frugal number, since it uses more digits than its factorization.

643966125625 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 64218 (or 32104 counting only the distinct ones).

The product of its digits is 13996800, while the sum is 55.

The spelling of 643966125625 in words is "six hundred forty-three billion, nine hundred sixty-six million, one hundred twenty-five thousand, six hundred twenty-five".