640620660 has 48 divisors (see below), whose sum is σ = 1800602496. Its totient is φ = 170178432.

The previous prime is 640620649. The next prime is 640620661. The reversal of 640620660 is 66026046.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (640620661) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 4519 + ... + 36078.

It is an arithmetic number, because the mean of its divisors is an integer number (37512552).

Almost surely, 2^640620660 is an apocalyptic number.

640620660 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

640620660 is an abundant number, since it is smaller than the sum of its proper divisors (1159981836).

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

640620660 is a wasteful number, since it uses less digits than its factorization.

640620660 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 40872 (or 40870 counting only the distinct ones).

The product of its (nonzero) digits is 10368, while the sum is 30.

The square root of 640620660 is about 25310.4851790715. The cubic root of 640620660 is about 862.0523633904.

The spelling of 640620660 in words is "six hundred forty million, six hundred twenty thousand, six hundred sixty".