640020645 has 24 divisors (see below), whose sum is σ = 1210221792. Its totient is φ = 310312800.

The previous prime is 640020611. The next prime is 640020659. The reversal of 640020645 is 546020046.

It is a happy number.

It is not a de Polignac number, because 640020645 - 2⁶ = 640020581 is a prime.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 645991 + ... + 646980.

It is an arithmetic number, because the mean of its divisors is an integer number (50425908).

Almost surely, 2^640020645 is an apocalyptic number.

It is an amenable number.

640020645 is a deficient number, since it is larger than the sum of its proper divisors (570201147).

640020645 is a wasteful number, since it uses less digits than its factorization.

640020645 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1292993 (or 1292990 counting only the distinct ones).

The product of its (nonzero) digits is 5760, while the sum is 27.

The square root of 640020645 is about 25298.6293106959. The cubic root of 640020645 is about 861.7831422265.

The spelling of 640020645 in words is "six hundred forty million, twenty thousand, six hundred forty-five".