640686377 has 4 divisors (see below), whose sum is σ = 656312916. Its totient is φ = 625059840.

The previous prime is 640686349. The next prime is 640686427. The reversal of 640686377 is 773686046.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 92236816 + 548449561 = 9604^2 + 23419^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-640686377 is a prime.

It is a super-2 number, since 2×640686377² = 820958067346772258, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (640686307) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 7813208 + ... + 7813289.

It is an arithmetic number, because the mean of its divisors is an integer number (164078229).

Almost surely, 2^640686377 is an apocalyptic number.

It is an amenable number.

640686377 is a deficient number, since it is larger than the sum of its proper divisors (15626539).

640686377 is a wasteful number, since it uses less digits than its factorization.

640686377 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15626538.

The product of its (nonzero) digits is 1016064, while the sum is 47.

The square root of 640686377 is about 25311.7833626949. The cubic root of 640686377 is about 862.0818397830.

The spelling of 640686377 in words is "six hundred forty million, six hundred eighty-six thousand, three hundred seventy-seven".