645515650 has 48 divisors (see below), whose sum is σ = 1295620200. Its totient is φ = 237864960.

The previous prime is 645515639. The next prime is 645515657. The reversal of 645515650 is 56515546.

It is a Cunningham number, because it is equal to 25407²+1.

It can be written as a sum of positive squares in 12 ways, for example, as 50594769 + 594920881 = 7113^2 + 24391^2 .

It is not an unprimeable number, because it can be changed into a prime (645515657) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 603316 + ... + 604384.

Almost surely, 2^645515650 is an apocalyptic number.

645515650 is an abundant number, since it is smaller than the sum of its proper divisors (650104550).

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

645515650 is a wasteful number, since it uses less digits than its factorization.

645515650 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2023 (or 2018 counting only the distinct ones).

The product of its (nonzero) digits is 90000, while the sum is 37.

The square root of 645515650 is about 25407.0000196796. Note that the first 4 decimals coincide. The cubic root of 645515650 is about 864.2424454288.

The spelling of 645515650 in words is "six hundred forty-five million, five hundred fifteen thousand, six hundred fifty".