638795532581 has 2 divisors, whose sum is σ = 638795532582. Its totient is φ = 638795532580.

The previous prime is 638795532547. The next prime is 638795532619. The reversal of 638795532581 is 185235597836.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 382182367681 + 256613164900 = 618209^2 + 506570^2 .

It is a cyclic number.

It is not a de Polignac number, because 638795532581 - 2²² = 638791338277 is a prime.

It is a super-2 number, since 2×638795532581² (a number of 24 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (638795531581) by changing a digit.

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 as a sum of consecutive naturals, namely, 319397766290 + 319397766291.

It is an arithmetic number, because the mean of its divisors is an integer number (319397766291).

Almost surely, 2^638795532581 is an apocalyptic number.

It is an amenable number.

638795532581 is a deficient number, since it is larger than the sum of its proper divisors (1).

638795532581 is an equidigital number, since it uses as much as digits as its factorization.

638795532581 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 54432000, while the sum is 62.

The spelling of 638795532581 in words is "six hundred thirty-eight billion, seven hundred ninety-five million, five hundred thirty-two thousand, five hundred eighty-one".