640764971 has 16 divisors (see below), whose sum is σ = 808995840. Its totient is φ = 492972480.

The previous prime is 640764967. The next prime is 640764977. The reversal of 640764971 is 179467046.

It is not a de Polignac number, because 640764971 - 2² = 640764967 is a prime.

It is a Smith number, since the sum of its digits (44) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (640764977) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 46586 + ... + 58751.

It is an arithmetic number, because the mean of its divisors is an integer number (50562240).

Almost surely, 2^640764971 is an apocalyptic number.

640764971 is a deficient number, since it is larger than the sum of its proper divisors (168230869).

640764971 is a wasteful number, since it uses less digits than its factorization.

640764971 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 105434.

The product of its (nonzero) digits is 254016, while the sum is 44.

The square root of 640764971 is about 25313.3358331137. The cubic root of 640764971 is about 862.1170893175.

The spelling of 640764971 in words is "six hundred forty million, seven hundred sixty-four thousand, nine hundred seventy-one".