638026777981 has 2 divisors, whose sum is σ = 638026777982. Its totient is φ = 638026777980.

The previous prime is 638026777979. The next prime is 638026778029. The reversal of 638026777981 is 189777620836.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 549835597081 + 88191180900 = 741509^2 + 296970^2 .

It is a cyclic number.

It is not a de Polignac number, because 638026777981 - 2¹ = 638026777979 is a prime.

It is a super-2 number, since 2×638026777981² (a number of 24 digits) contains 22 as substring.

Together with 638026777979, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (638026777781) 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, 319013388990 + 319013388991.

It is an arithmetic number, because the mean of its divisors is an integer number (319013388991).

Almost surely, 2^638026777981 is an apocalyptic number.

It is an amenable number.

638026777981 is a deficient number, since it is larger than the sum of its proper divisors (1).

638026777981 is an equidigital number, since it uses as much as digits as its factorization.

638026777981 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 42674688, while the sum is 64.

The spelling of 638026777981 in words is "six hundred thirty-eight billion, twenty-six million, seven hundred seventy-seven thousand, nine hundred eighty-one".