645635720 has 16 divisors (see below), whose sum is σ = 1452680460. Its totient is φ = 258254272.

The previous prime is 645635719. The next prime is 645635723. The reversal of 645635720 is 27536546.

It can be written as a sum of positive squares in 2 ways, for example, as 597998116 + 47637604 = 24454^2 + 6902^2 .

It is not an unprimeable number, because it can be changed into a prime (645635723) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 8070407 + ... + 8070486.

Almost surely, 2^645635720 is an apocalyptic number.

It is an amenable number.

645635720 is an abundant number, since it is smaller than the sum of its proper divisors (807044740).

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

645635720 is a wasteful number, since it uses less digits than its factorization.

645635720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16140904 (or 16140900 counting only the distinct ones).

The product of its (nonzero) digits is 151200, while the sum is 38.

The square root of 645635720 is about 25409.3628412835. The cubic root of 645635720 is about 864.2960269633.

The spelling of 645635720 in words is "six hundred forty-five million, six hundred thirty-five thousand, seven hundred twenty".