645704257665 has 16 divisors (see below), whose sum is σ = 1033331472576. Its totient is φ = 344307384000.

The previous prime is 645704257663. The next prime is 645704257697. The reversal of 645704257665 is 566752407546.

It is not a de Polignac number, because 645704257665 - 2¹ = 645704257663 is a prime.

It is a super-2 number, since 2×645704257665² (a number of 24 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (645704257663) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 4185466 + ... + 4336995.

It is an arithmetic number, because the mean of its divisors is an integer number (64583217036).

Almost surely, 2^645704257665 is an apocalyptic number.

It is an amenable number.

645704257665 is a deficient number, since it is larger than the sum of its proper divisors (387627214911).

645704257665 is a wasteful number, since it uses less digits than its factorization.

645704257665 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8527520.

The product of its (nonzero) digits is 42336000, while the sum is 57.

The spelling of 645704257665 in words is "six hundred forty-five billion, seven hundred four million, two hundred fifty-seven thousand, six hundred sixty-five".