640706988 has 18 divisors (see below), whose sum is σ = 1495187596. Its totient is φ = 213539768.

The previous prime is 640706981. The next prime is 640707007. The reversal of 640706988 is 889607046.

It is not an unprimeable number, because it can be changed into a prime (640706981) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 84031 + ... + 91337.

Almost surely, 2^640706988 is an apocalyptic number.

It is an amenable number.

640706988 is an abundant number, since it is smaller than the sum of its proper divisors (854480608).

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

640706988 is an frugal number, since it uses more digits than its factorization.

640706988 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 14621 (or 7312 counting only the distinct ones).

The product of its (nonzero) digits is 580608, while the sum is 48.

The square root of 640706988 is about 25312.1905018116. The cubic root of 640706988 is about 862.0910841282.

Multiplying 640706988 by its sum of digits (48), we get a square (30753935424 = 175368²).

The spelling of 640706988 in words is "six hundred forty million, seven hundred six thousand, nine hundred eighty-eight".