638968857 has 4 divisors (see below), whose sum is σ = 851958480. Its totient is φ = 425979236.

The previous prime is 638968849. The next prime is 638968859. The reversal of 638968857 is 758869836.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 638968857 - 2³ = 638968849 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 638968857.

It is not an unprimeable number, because it can be changed into a prime (638968859) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 106494807 + ... + 106494812.

It is an arithmetic number, because the mean of its divisors is an integer number (212989620).

Almost surely, 2^638968857 is an apocalyptic number.

It is an amenable number.

638968857 is a deficient number, since it is larger than the sum of its proper divisors (212989623).

638968857 is a wasteful number, since it uses less digits than its factorization.

638968857 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 212989622.

The product of its digits is 17418240, while the sum is 60.

The square root of 638968857 is about 25277.8333130037. The cubic root of 638968857 is about 861.3108084295.

The spelling of 638968857 in words is "six hundred thirty-eight million, nine hundred sixty-eight thousand, eight hundred fifty-seven".