640139844 has 24 divisors (see below), whose sum is σ = 1512568960. Its totient is φ = 210678624.

The previous prime is 640139837. The next prime is 640139861. The reversal of 640139844 is 448931046.

It is a happy number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 336679 + ... + 338574.

Almost surely, 2^640139844 is an apocalyptic number.

It is an amenable number.

640139844 is an abundant number, since it is smaller than the sum of its proper divisors (872429116).

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

640139844 is a wasteful number, since it uses less digits than its factorization.

640139844 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 675339 (or 675337 counting only the distinct ones).

The product of its (nonzero) digits is 82944, while the sum is 39.

The square root of 640139844 is about 25300.9850401126. The cubic root of 640139844 is about 861.8366391009.

The spelling of 640139844 in words is "six hundred forty million, one hundred thirty-nine thousand, eight hundred forty-four".