640644660420 has 48 divisors (see below), whose sum is σ = 1804810015680. Its totient is φ = 169790484096.

The previous prime is 640644660413. The next prime is 640644660421. The reversal of 640644660420 is 24066446046.

It is a super-2 number, since 2×640644660420² (a number of 24 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (640644660421) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 32743015 + ... + 32762574.

It is an arithmetic number, because the mean of its divisors is an integer number (37600208660).

Almost surely, 2^640644660420 is an apocalyptic number.

640644660420 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

640644660420 is an abundant number, since it is smaller than the sum of its proper divisors (1164165355260).

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

640644660420 is a wasteful number, since it uses less digits than its factorization.

640644660420 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 65505764 (or 65505762 counting only the distinct ones).

The product of its (nonzero) digits is 663552, while the sum is 42.

The spelling of 640644660420 in words is "six hundred forty billion, six hundred forty-four million, six hundred sixty thousand, four hundred twenty".