638249879 has 2 divisors, whose sum is σ = 638249880. Its totient is φ = 638249878.

The previous prime is 638249873. The next prime is 638249897. The reversal of 638249879 is 978942836.

It is a happy number.

Together with next prime (638249897) it forms an Ormiston pair, because they use the same digits, order apart.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-638249879 is a prime.

It is a Sophie Germain prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (638249873) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 319124939 + 319124940.

It is an arithmetic number, because the mean of its divisors is an integer number (319124940).

Almost surely, 2^638249879 is an apocalyptic number.

638249879 is a deficient number, since it is larger than the sum of its proper divisors (1).

638249879 is an equidigital number, since it uses as much as digits as its factorization.

638249879 is an evil number, because the sum of its binary digits is even.

The product of its digits is 5225472, while the sum is 56.

The square root of 638249879 is about 25263.6077985707. The cubic root of 638249879 is about 860.9876336095.

The spelling of 638249879 in words is "six hundred thirty-eight million, two hundred forty-nine thousand, eight hundred seventy-nine".