640681767 has 96 divisors (see below), whose sum is σ = 1132185600. Its totient is φ = 344520000.

The previous prime is 640681757. The next prime is 640681781. The reversal of 640681767 is 767186046.

It is not a de Polignac number, because 640681767 - 2¹⁶ = 640616231 is a prime.

It is a Smith number, since the sum of its digits (45) coincides with the sum of the digits of its prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (640681757) by changing a digit.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 2552392 + ... + 2552642.

It is an arithmetic number, because the mean of its divisors is an integer number (11793600).

Almost surely, 2^640681767 is an apocalyptic number.

640681767 is a deficient number, since it is larger than the sum of its proper divisors (491503833).

640681767 is a wasteful number, since it uses less digits than its factorization.

640681767 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 369 (or 366 counting only the distinct ones).

The product of its (nonzero) digits is 338688, while the sum is 45.

The square root of 640681767 is about 25311.6922982245. The cubic root of 640681767 is about 862.0797721011.

The spelling of 640681767 in words is "six hundred forty million, six hundred eighty-one thousand, seven hundred sixty-seven".