640689240 has 32 divisors (see below), whose sum is σ = 1922068080. Its totient is φ = 170850432.

The previous prime is 640689233. The next prime is 640689241. The reversal of 640689240 is 42986046.

640689240 is digitally balanced in base 6, because in such base it contains all the possibile digits an equal number of times.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (640689241) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2669419 + ... + 2669658.

Almost surely, 2^640689240 is an apocalyptic number.

640689240 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

640689240 is an abundant number, since it is smaller than the sum of its proper divisors (1281378840).

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

640689240 is a wasteful number, since it uses less digits than its factorization.

640689240 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5339091 (or 5339087 counting only the distinct ones).

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

The square root of 640689240 is about 25311.8399173193. The cubic root of 640689240 is about 862.0831238936.

The spelling of 640689240 in words is "six hundred forty million, six hundred eighty-nine thousand, two hundred forty".