640645767 has 20 divisors (see below), whose sum is σ = 977381856. Its totient is φ = 418007520.

The previous prime is 640645741. The next prime is 640645769. The reversal of 640645767 is 767546046.

It is a happy number.

It is not a de Polignac number, because 640645767 - 2¹¹ = 640643719 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (640645769) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 80334 + ... + 87947.

Almost surely, 2^640645767 is an apocalyptic number.

640645767 is a deficient number, since it is larger than the sum of its proper divisors (336736089).

640645767 is a wasteful number, since it uses less digits than its factorization.

640645767 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 168340 (or 168331 counting only the distinct ones).

The product of its (nonzero) digits is 846720, while the sum is 45.

The square root of 640645767 is about 25310.9811544318. The cubic root of 640645767 is about 862.0636250035.

The spelling of 640645767 in words is "six hundred forty million, six hundred forty-five thousand, seven hundred sixty-seven".