640436646631 has 4 divisors (see below), whose sum is σ = 641022591592. Its totient is φ = 639850701672.

The previous prime is 640436646581. The next prime is 640436646659. The reversal of 640436646631 is 136646634046.

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

It is a cyclic number.

It is not a de Polignac number, because 640436646631 - 2²¹ = 640434549479 is a prime.

It is a super-2 number, since 2×640436646631² (a number of 24 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (640436646431) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 292970841 + ... + 292973026.

It is an arithmetic number, because the mean of its divisors is an integer number (160255647898).

Almost surely, 2^640436646631 is an apocalyptic number.

640436646631 is a deficient number, since it is larger than the sum of its proper divisors (585944961).

640436646631 is a wasteful number, since it uses less digits than its factorization.

640436646631 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 585944960.

The product of its (nonzero) digits is 4478976, while the sum is 49.

The spelling of 640436646631 in words is "six hundred forty billion, four hundred thirty-six million, six hundred forty-six thousand, six hundred thirty-one".