638509891447 has 2 divisors, whose sum is σ = 638509891448. Its totient is φ = 638509891446.

The previous prime is 638509891387. The next prime is 638509891451. The reversal of 638509891447 is 744198905836.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 638509891447 - 2²³ = 638501502839 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (638509891847) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 319254945723 + 319254945724.

It is an arithmetic number, because the mean of its divisors is an integer number (319254945724).

Almost surely, 2^638509891447 is an apocalyptic number.

638509891447 is a deficient number, since it is larger than the sum of its proper divisors (1).

638509891447 is an equidigital number, since it uses as much as digits as its factorization.

638509891447 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 52254720, while the sum is 64.

The spelling of 638509891447 in words is "six hundred thirty-eight billion, five hundred nine million, eight hundred ninety-one thousand, four hundred forty-seven".