645725961 has 12 divisors (see below), whose sum is σ = 957924292. Its totient is φ = 418849056.

The previous prime is 645725959. The next prime is 645725987. The reversal of 645725961 is 169527546.

645725961 is a `hidden beast` number, since 6 + 4 + 57 + 2 + 596 + 1 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 495908361 + 149817600 = 22269^2 + 12240^2 .

It is not a de Polignac number, because 645725961 - 2¹ = 645725959 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (645725921) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 969226 + ... + 969891.

Almost surely, 2^645725961 is an apocalyptic number.

It is an amenable number.

645725961 is a deficient number, since it is larger than the sum of its proper divisors (312198331).

645725961 is a wasteful number, since it uses less digits than its factorization.

645725961 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1939160 (or 1939157 counting only the distinct ones).

The product of its digits is 453600, while the sum is 45.

The square root of 645725961 is about 25411.1385223095. The cubic root of 645725961 is about 864.3362928603.

The spelling of 645725961 in words is "six hundred forty-five million, seven hundred twenty-five thousand, nine hundred sixty-one".