640256128 has 16 divisors (see below), whose sum is σ = 1275510510. Its totient is φ = 320128000.

The previous prime is 640256047. The next prime is 640256131. The reversal of 640256128 is 821652046.

It can be written as a sum of positive squares in only one way, i.e., 576384064 + 63872064 = 24008^2 + 7992^2 .

It is a tau number, because it is divible by the number of its divisors (16).

It is a junction number, because it is equal to n+sod(n) for n = 640256093 and 640256102.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2500873 + ... + 2501128.

Almost surely, 2^640256128 is an apocalyptic number.

It is an amenable number.

640256128 is a deficient number, since it is larger than the sum of its proper divisors (635254382).

640256128 is an equidigital number, since it uses as much as digits as its factorization.

640256128 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5002015 (or 5002003 counting only the distinct ones).

The product of its (nonzero) digits is 23040, while the sum is 34.

The square root of 640256128 is about 25303.2829490562. The cubic root of 640256128 is about 861.8888213155. Note that the first 4 decimals are identical.

The spelling of 640256128 in words is "six hundred forty million, two hundred fifty-six thousand, one hundred twenty-eight".