640720128 has 108 divisors (see below), whose sum is σ = 1800502368. Its totient is φ = 202245120.

The previous prime is 640720111. The next prime is 640720133. The reversal of 640720128 is 821027046.

It is a junction number, because it is equal to n+sod(n) for n = 640720095 and 640720104.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 276093 + ... + 278403.

Almost surely, 2^640720128 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 640720128, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (900251184).

640720128 is an abundant number, since it is smaller than the sum of its proper divisors (1159782240).

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

640720128 is a wasteful number, since it uses less digits than its factorization.

640720128 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2368 (or 2335 counting only the distinct ones).

The product of its (nonzero) digits is 5376, while the sum is 30.

The square root of 640720128 is about 25312.4500592100. The cubic root of 640720128 is about 862.0969775135.

The spelling of 640720128 in words is "six hundred forty million, seven hundred twenty thousand, one hundred twenty-eight".