640661128 has 32 divisors (see below), whose sum is σ = 1268847360. Its totient is φ = 302783040.

The previous prime is 640661093. The next prime is 640661129. The reversal of 640661128 is 821166046.

640661128 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a junction number, because it is equal to n+sod(n) for n = 640661093 and 640661102.

It is not an unprimeable number, because it can be changed into a prime (640661129) 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, 19375 + ... + 40702.

It is an arithmetic number, because the mean of its divisors is an integer number (39651480).

Almost surely, 2^640661128 is an apocalyptic number.

It is an amenable number.

640661128 is a deficient number, since it is larger than the sum of its proper divisors (628186232).

640661128 is a wasteful number, since it uses less digits than its factorization.

640661128 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 60157 (or 60153 counting only the distinct ones).

The product of its (nonzero) digits is 13824, while the sum is 34.

The square root of 640661128 is about 25311.2845979812. The cubic root of 640661128 is about 862.0705149543.

The spelling of 640661128 in words is "six hundred forty million, six hundred sixty-one thousand, one hundred twenty-eight".