638634626781 has 8 divisors (see below), whose sum is σ = 851518365984. Its totient is φ = 425753652720.

The previous prime is 638634626737. The next prime is 638634626789. The reversal of 638634626781 is 187626436836.

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

It is not a de Polignac number, because 638634626781 - 2¹⁹ = 638634102493 is a prime.

It is a super-2 number, since 2×638634626781² (a number of 24 digits) contains 22 as substring.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (638634626789) 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, 73510 + ... + 1132551.

It is an arithmetic number, because the mean of its divisors is an integer number (106439795748).

Almost surely, 2^638634626781 is an apocalyptic number.

It is an amenable number.

638634626781 is a deficient number, since it is larger than the sum of its proper divisors (212883739203).

638634626781 is a wasteful number, since it uses less digits than its factorization.

638634626781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1382571.

The product of its digits is 41803776, while the sum is 60.

The spelling of 638634626781 in words is "six hundred thirty-eight billion, six hundred thirty-four million, six hundred twenty-six thousand, seven hundred eighty-one".