638636188121 has 4 divisors (see below), whose sum is σ = 638638897152. Its totient is φ = 638633479092.

The previous prime is 638636188093. The next prime is 638636188139. The reversal of 638636188121 is 121881636836.

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 638636188121 - 2¹⁴ = 638636171737 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (638636187121) 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, 963221 + ... + 1484946.

It is an arithmetic number, because the mean of its divisors is an integer number (159659724288).

Almost surely, 2^638636188121 is an apocalyptic number.

It is an amenable number.

638636188121 is a deficient number, since it is larger than the sum of its proper divisors (2709031).

638636188121 is a wasteful number, since it uses less digits than its factorization.

638636188121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2709030.

The product of its digits is 1990656, while the sum is 53.

The spelling of 638636188121 in words is "six hundred thirty-eight billion, six hundred thirty-six million, one hundred eighty-eight thousand, one hundred twenty-one".