645668857 has 16 divisors (see below), whose sum is σ = 714776832. Its totient is φ = 580124160.

The previous prime is 645668851. The next prime is 645668921. The reversal of 645668857 is 758866546.

It is a cyclic number.

It is not a de Polignac number, because 645668857 - 2¹⁹ = 645144569 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 645668798 and 645668807.

It is not an unprimeable number, because it can be changed into a prime (645668851) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 245413 + ... + 248029.

It is an arithmetic number, because the mean of its divisors is an integer number (44673552).

Almost surely, 2^645668857 is an apocalyptic number.

It is an amenable number.

645668857 is a deficient number, since it is larger than the sum of its proper divisors (69107975).

645668857 is a wasteful number, since it uses less digits than its factorization.

645668857 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3288.

The product of its digits is 9676800, while the sum is 55.

The square root of 645668857 is about 25410.0148957060. The cubic root of 645668857 is about 864.3108132618.

The spelling of 645668857 in words is "six hundred forty-five million, six hundred sixty-eight thousand, eight hundred fifty-seven".