638680691261 has 8 divisors (see below), whose sum is σ = 672677918784. Its totient is φ = 605202505600.

The previous prime is 638680691249. The next prime is 638680691281. The reversal of 638680691261 is 162196086836.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 638680691261 - 2⁶ = 638680691197 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 638680691197 and 638680691206.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (638680691281) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 129757940 + ... + 129762861.

It is an arithmetic number, because the mean of its divisors is an integer number (84084739848).

Almost surely, 2^638680691261 is an apocalyptic number.

It is an amenable number.

638680691261 is a deficient number, since it is larger than the sum of its proper divisors (33997227523).

638680691261 is a wasteful number, since it uses less digits than its factorization.

638680691261 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 259520931.

The product of its (nonzero) digits is 4478976, while the sum is 56.

The spelling of 638680691261 in words is "six hundred thirty-eight billion, six hundred eighty million, six hundred ninety-one thousand, two hundred sixty-one".