645252665 has 4 divisors (see below), whose sum is σ = 774303204. Its totient is φ = 516202128.

The previous prime is 645252653. The next prime is 645252701. The reversal of 645252665 is 566252546.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 486820096 + 158432569 = 22064^2 + 12587^2 .

It is a cyclic number.

It is not a de Polignac number, because 645252665 - 2¹⁰ = 645251641 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 64525262 + ... + 64525271.

It is an arithmetic number, because the mean of its divisors is an integer number (193575801).

Almost surely, 2^645252665 is an apocalyptic number.

It is an amenable number.

645252665 is a deficient number, since it is larger than the sum of its proper divisors (129050539).

645252665 is a wasteful number, since it uses less digits than its factorization.

645252665 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 129050538.

The product of its digits is 432000, while the sum is 41.

The square root of 645252665 is about 25401.8240486781. The cubic root of 645252665 is about 864.1250645041.

The spelling of 645252665 in words is "six hundred forty-five million, two hundred fifty-two thousand, six hundred sixty-five".