640690785 has 24 divisors (see below), whose sum is σ = 1269178560. Its totient is φ = 292887072.

The previous prime is 640690769. The next prime is 640690801. The reversal of 640690785 is 587096046.

It is an interprime number because it is at equal distance from previous prime (640690769) and next prime (640690801).

It is not a de Polignac number, because 640690785 - 2⁴ = 640690769 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a self number, because there is not a number n which added to its sum of digits gives 640690785.

It is an unprimeable number.

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 23 ways as a sum of consecutive naturals, for example, 1016655 + ... + 1017284.

It is an arithmetic number, because the mean of its divisors is an integer number (52882440).

Almost surely, 2^640690785 is an apocalyptic number.

It is an amenable number.

640690785 is a deficient number, since it is larger than the sum of its proper divisors (628487775).

640690785 is a wasteful number, since it uses less digits than its factorization.

640690785 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2033957 (or 2033954 counting only the distinct ones).

The product of its (nonzero) digits is 362880, while the sum is 45.

The square root of 640690785 is about 25311.8704366153. The cubic root of 640690785 is about 862.0838168543.

The spelling of 640690785 in words is "six hundred forty million, six hundred ninety thousand, seven hundred eighty-five".