640312817 has 2 divisors, whose sum is σ = 640312818. Its totient is φ = 640312816.

The previous prime is 640312763. The next prime is 640312823. The reversal of 640312817 is 718213046.

640312817 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 562590961 + 77721856 = 23719^2 + 8816^2 .

It is a cyclic number.

It is not a de Polignac number, because 640312817 - 2⁶ = 640312753 is a prime.

It is a super-2 number, since 2×640312817² = 820001007228950978, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (640312877) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 320156408 + 320156409.

It is an arithmetic number, because the mean of its divisors is an integer number (320156409).

Almost surely, 2^640312817 is an apocalyptic number.

It is an amenable number.

640312817 is a deficient number, since it is larger than the sum of its proper divisors (1).

640312817 is an equidigital number, since it uses as much as digits as its factorization.

640312817 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 8064, while the sum is 32.

The square root of 640312817 is about 25304.4031148731. The cubic root of 640312817 is about 861.9142581010.

The spelling of 640312817 in words is "six hundred forty million, three hundred twelve thousand, eight hundred seventeen".