638404639 has 2 divisors, whose sum is σ = 638404640. Its totient is φ = 638404638.

The previous prime is 638404633. The next prime is 638404643. The reversal of 638404639 is 936404836.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 638404639 - 2³ = 638404631 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 638404595 and 638404604.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (638404631) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 319202319 + 319202320.

It is an arithmetic number, because the mean of its divisors is an integer number (319202320).

Almost surely, 2^638404639 is an apocalyptic number.

638404639 is a deficient number, since it is larger than the sum of its proper divisors (1).

638404639 is an equidigital number, since it uses as much as digits as its factorization.

638404639 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 373248, while the sum is 43.

The square root of 638404639 is about 25266.6705167103. The cubic root of 638404639 is about 861.0572174733.

The spelling of 638404639 in words is "six hundred thirty-eight million, four hundred four thousand, six hundred thirty-nine".