645664157615 has 16 divisors (see below), whose sum is σ = 821997649920. Its totient is φ = 485492343840.

The previous prime is 645664157587. The next prime is 645664157623. The reversal of 645664157615 is 516751466546.

It is a happy number.

It is not a de Polignac number, because 645664157615 - 2¹⁴ = 645664141231 is a prime.

It is a Smith number, since the sum of its digits (56) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 26745671 + ... + 26769800.

It is an arithmetic number, because the mean of its divisors is an integer number (51374853120).

Almost surely, 2^645664157615 is an apocalyptic number.

645664157615 is a deficient number, since it is larger than the sum of its proper divisors (176333492305).

645664157615 is a wasteful number, since it uses less digits than its factorization.

645664157615 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 53515622.

The product of its digits is 18144000, while the sum is 56.

The spelling of 645664157615 in words is "six hundred forty-five billion, six hundred sixty-four million, one hundred fifty-seven thousand, six hundred fifteen".