640700928 has 200 divisors, whose sum is σ = 2186502912. Its totient is φ = 182974464.

The previous prime is 640700911. The next prime is 640701037. The reversal of 640700928 is 829007046.

640700928 is a `hidden beast` number, since 640 + 7 + 0 + 0 + 9 + 2 + 8 = 666.

It is a super-2 number, since 2×640700928² = 820995358280122368, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a junction number, because it is equal to n+sod(n) for n = 640700892 and 640700901.

It is an unprimeable number.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 289201 + ... + 291407.

Almost surely, 2^640700928 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 640700928, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1093251456).

640700928 is an abundant number, since it is smaller than the sum of its proper divisors (1545801984).

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

640700928 is an equidigital number, since it uses as much as digits as its factorization.

640700928 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2244 (or 2219 counting only the distinct ones).

The product of its (nonzero) digits is 24192, while the sum is 36.

The square root of 640700928 is about 25312.0707963612. The cubic root of 640700928 is about 862.0883661472.

The spelling of 640700928 in words is "six hundred forty million, seven hundred thousand, nine hundred twenty-eight".