640701636 has 12 divisors (see below), whose sum is σ = 1494970512. Its totient is φ = 213567208.

The previous prime is 640701631. The next prime is 640701643. The reversal of 640701636 is 636107046.

It is a tau number, because it is divible by the number of its divisors (12).

It is a junction number, because it is equal to n+sod(n) for n = 640701597 and 640701606.

It is not an unprimeable number, because it can be changed into a prime (640701631) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 26695890 + ... + 26695913.

It is an arithmetic number, because the mean of its divisors is an integer number (124580876).

Almost surely, 2^640701636 is an apocalyptic number.

It is an amenable number.

640701636 is an abundant number, since it is smaller than the sum of its proper divisors (854268876).

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

640701636 is a wasteful number, since it uses less digits than its factorization.

640701636 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 53391810 (or 53391808 counting only the distinct ones).

The product of its (nonzero) digits is 18144, while the sum is 33.

The square root of 640701636 is about 25312.0847817796. The cubic root of 640701636 is about 862.0886836943.

The spelling of 640701636 in words is "six hundred forty million, seven hundred one thousand, six hundred thirty-six".