638865520085 has 16 divisors (see below), whose sum is σ = 825748680960. Its totient is φ = 471698840640.

The previous prime is 638865520009. The next prime is 638865520093. The reversal of 638865520085 is 580025568836.

It is not a de Polignac number, because 638865520085 - 2²⁶ = 638798411221 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 638865520085.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 426845 + ... + 1208274.

It is an arithmetic number, because the mean of its divisors is an integer number (51609292560).

Almost surely, 2^638865520085 is an apocalyptic number.

638865520085 is a gapful number since it is divisible by the number (65) formed by its first and last digit.

It is an amenable number.

638865520085 is a deficient number, since it is larger than the sum of its proper divisors (186883160875).

638865520085 is a wasteful number, since it uses less digits than its factorization.

638865520085 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1641148.

The product of its (nonzero) digits is 13824000, while the sum is 56.

The spelling of 638865520085 in words is "six hundred thirty-eight billion, eight hundred sixty-five million, five hundred twenty thousand, eighty-five".