640523628 has 36 divisors (see below), whose sum is σ = 1634830288. Its totient is φ = 211433760.

The previous prime is 640523623. The next prime is 640523629. The reversal of 640523628 is 826325046.

640523628 is a `hidden beast` number, since 6 + 4 + 0 + 5 + 23 + 628 = 666.

It is a tau number, because it is divible by the number of its divisors (36).

It is a Smith number, since the sum of its digits (36) coincides with the sum of the digits of its prime factors.

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 = 640523592 and 640523601.

It is not an unprimeable number, because it can be changed into a prime (640523621) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 82663 + ... + 90078.

Almost surely, 2^640523628 is an apocalyptic number.

It is an amenable number.

640523628 is an abundant number, since it is smaller than the sum of its proper divisors (994306660).

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

640523628 is a wasteful number, since it uses less digits than its factorization.

640523628 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 172854 (or 172849 counting only the distinct ones).

The product of its (nonzero) digits is 69120, while the sum is 36.

The square root of 640523628 is about 25308.5682724251. The cubic root of 640523628 is about 862.0088374300.

The spelling of 640523628 in words is "six hundred forty million, five hundred twenty-three thousand, six hundred twenty-eight".