640621660 has 24 divisors (see below), whose sum is σ = 1537492320. Its totient is φ = 219641664.

The previous prime is 640621649. The next prime is 640621669. The reversal of 640621660 is 66126046.

640621660 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a super-2 number, since 2×640621660² = 820792222522311200, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (640621669) 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, 2287795 + ... + 2288074.

It is an arithmetic number, because the mean of its divisors is an integer number (64062180).

Almost surely, 2^640621660 is an apocalyptic number.

It is an amenable number.

640621660 is an abundant number, since it is smaller than the sum of its proper divisors (896870660).

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

640621660 is a wasteful number, since it uses less digits than its factorization.

640621660 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4575885 (or 4575883 counting only the distinct ones).

The product of its (nonzero) digits is 10368, while the sum is 31.

The square root of 640621660 is about 25310.5049337227. The cubic root of 640621660 is about 862.0528119408.

The spelling of 640621660 in words is "six hundred forty million, six hundred twenty-one thousand, six hundred sixty".