638657218841 has 6 divisors (see below), whose sum is σ = 667632216090. Its totient is φ = 610889513168.

The previous prime is 638657218831. The next prime is 638657218867. The reversal of 638657218841 is 148812756836.

It can be written as a sum of positive squares in only one way, i.e., 484388160400 + 154269058441 = 695980^2 + 392771^2 .

It is not a de Polignac number, because 638657218841 - 2³⁰ = 637583477017 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (638657218831) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 603645236 + ... + 603646293.

It is an arithmetic number, because the mean of its divisors is an integer number (111272036015).

Almost surely, 2^638657218841 is an apocalyptic number.

It is an amenable number.

638657218841 is a deficient number, since it is larger than the sum of its proper divisors (28974997249).

638657218841 is a wasteful number, since it uses less digits than its factorization.

638657218841 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1207291575 (or 1207291552 counting only the distinct ones).

The product of its digits is 15482880, while the sum is 59.

The spelling of 638657218841 in words is "six hundred thirty-eight billion, six hundred fifty-seven million, two hundred eighteen thousand, eight hundred forty-one".