640735686 has 24 divisors (see below), whose sum is σ = 1436132880. Its totient is φ = 206213616.

The previous prime is 640735609. The next prime is 640735687. The reversal of 640735686 is 686537046.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (640735687) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 613210 + ... + 614253.

It is an arithmetic number, because the mean of its divisors is an integer number (59838870).

Almost surely, 2^640735686 is an apocalyptic number.

640735686 is an abundant number, since it is smaller than the sum of its proper divisors (795397194).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

640735686 is a wasteful number, since it uses less digits than its factorization.

640735686 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1227500 (or 1227497 counting only the distinct ones).

The product of its (nonzero) digits is 725760, while the sum is 45.

The square root of 640735686 is about 25312.7573764693. The cubic root of 640735686 is about 862.1039552852.

The spelling of 640735686 in words is "six hundred forty million, seven hundred thirty-five thousand, six hundred eighty-six".