638074781 has 2 divisors, whose sum is σ = 638074782. Its totient is φ = 638074780.

The previous prime is 638074751. The next prime is 638074783. The reversal of 638074781 is 187470836.

638074781 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 488012281 + 150062500 = 22091^2 + 12250^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-638074781 is a prime.

It is a super-2 number, since 2×638074781² = 814278852296395922, which contains 22 as substring.

Together with 638074783, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (638074783) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 319037390 + 319037391.

It is an arithmetic number, because the mean of its divisors is an integer number (319037391).

Almost surely, 2^638074781 is an apocalyptic number.

It is an amenable number.

638074781 is a deficient number, since it is larger than the sum of its proper divisors (1).

638074781 is an equidigital number, since it uses as much as digits as its factorization.

638074781 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 225792, while the sum is 44.

The square root of 638074781 is about 25260.1421413261. The cubic root of 638074781 is about 860.9088917217.

The spelling of 638074781 in words is "six hundred thirty-eight million, seventy-four thousand, seven hundred eighty-one".