638523857 has 4 divisors (see below), whose sum is σ = 638577060. Its totient is φ = 638470656.

The previous prime is 638523841. The next prime is 638523863. The reversal of 638523857 is 758325836.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 512388496 + 126135361 = 22636^2 + 11231^2 .

It is a cyclic number.

It is not a de Polignac number, because 638523857 - 2⁴ = 638523841 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (638523877) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 833 + ... + 35745.

It is an arithmetic number, because the mean of its divisors is an integer number (159644265).

Almost surely, 2^638523857 is an apocalyptic number.

It is an amenable number.

638523857 is a deficient number, since it is larger than the sum of its proper divisors (53203).

638523857 is a wasteful number, since it uses less digits than its factorization.

638523857 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 53202.

The product of its digits is 1209600, while the sum is 47.

The square root of 638523857 is about 25269.0296014707. The cubic root of 638523857 is about 861.1108131208.

The spelling of 638523857 in words is "six hundred thirty-eight million, five hundred twenty-three thousand, eight hundred fifty-seven".