640694440 has 64 divisors (see below), whose sum is σ = 1583452800. Its totient is φ = 232227072.

The previous prime is 640694437. The next prime is 640694471. The reversal of 640694440 is 44496046.

It is a self number, because there is not a number n which added to its sum of digits gives 640694440.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 847 + ... + 35806.

It is an arithmetic number, because the mean of its divisors is an integer number (24741450).

Almost surely, 2^640694440 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 640694440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (791726400).

640694440 is an abundant number, since it is smaller than the sum of its proper divisors (942758360).

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

640694440 is a wasteful number, since it uses less digits than its factorization.

640694440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 36706 (or 36702 counting only the distinct ones).

The product of its (nonzero) digits is 82944, while the sum is 37.

The square root of 640694440 is about 25311.9426358389. The cubic root of 640694440 is about 862.0854561840.

The spelling of 640694440 in words is "six hundred forty million, six hundred ninety-four thousand, four hundred forty".