638784657 has 64 divisors (see below), whose sum is σ = 1107025920. Its totient is φ = 356529600.

The previous prime is 638784649. The next prime is 638784659. The reversal of 638784657 is 756487836.

It is not a de Polignac number, because 638784657 - 2³ = 638784649 is a prime.

It is not an unprimeable number, because it can be changed into a prime (638784659) 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 63 ways as a sum of consecutive naturals, for example, 2428708 + ... + 2428970.

It is an arithmetic number, because the mean of its divisors is an integer number (17297280).

Almost surely, 2^638784657 is an apocalyptic number.

It is an amenable number.

638784657 is a deficient number, since it is larger than the sum of its proper divisors (468241263).

638784657 is a wasteful number, since it uses less digits than its factorization.

638784657 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 531 (or 525 counting only the distinct ones).

The product of its digits is 6773760, while the sum is 54.

The square root of 638784657 is about 25274.1895419022. The cubic root of 638784657 is about 861.2280351211.

The spelling of 638784657 in words is "six hundred thirty-eight million, seven hundred eighty-four thousand, six hundred fifty-seven".