640355857 has 16 divisors (see below), whose sum is σ = 686027520. Its totient is φ = 596376000.

The previous prime is 640355827. The next prime is 640355861. The reversal of 640355857 is 758553046.

It is a cyclic number.

It is not a de Polignac number, because 640355857 - 2¹¹ = 640353809 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (640355827) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 139444 + ... + 143962.

It is an arithmetic number, because the mean of its divisors is an integer number (42876720).

Almost surely, 2^640355857 is an apocalyptic number.

It is an amenable number.

640355857 is a deficient number, since it is larger than the sum of its proper divisors (45671663).

640355857 is a wasteful number, since it uses less digits than its factorization.

640355857 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4704.

The product of its (nonzero) digits is 504000, while the sum is 43.

The square root of 640355857 is about 25305.2535454597. The cubic root of 640355857 is about 861.9335694738.

The spelling of 640355857 in words is "six hundred forty million, three hundred fifty-five thousand, eight hundred fifty-seven".