18639138640 has 40 divisors (see below), whose sum is σ = 45885177000. Its totient is φ = 7017086976.

The previous prime is 18639138629. The next prime is 18639138671. The reversal of 18639138640 is 4683193681.

It can be written as a sum of positive squares in 4 ways, for example, as 2757090064 + 15882048576 = 52508^2 + 126024^2 .

It is a tau number, because it is divible by the number of its divisors (40).

It is a super-2 number, since 2×18639138640² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 6851265 + ... + 6853984.

It is an arithmetic number, because the mean of its divisors is an integer number (1147129425).

Almost surely, 2^18639138640 is an apocalyptic number.

18639138640 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

18639138640 is an abundant number, since it is smaller than the sum of its proper divisors (27246038360).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

18639138640 is a wasteful number, since it uses less digits than its factorization.

18639138640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13705279 (or 13705273 counting only the distinct ones).

The product of its (nonzero) digits is 746496, while the sum is 49.

The spelling of 18639138640 in words is "eighteen billion, six hundred thirty-nine million, one hundred thirty-eight thousand, six hundred forty".