639686423 has 2 divisors, whose sum is σ = 639686424. Its totient is φ = 639686422.

The previous prime is 639686413. The next prime is 639686441. The reversal of 639686423 is 324686936.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 639686423 - 2⁴ = 639686407 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (639686413) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 319843211 + 319843212.

It is an arithmetic number, because the mean of its divisors is an integer number (319843212).

Almost surely, 2^639686423 is an apocalyptic number.

639686423 is a deficient number, since it is larger than the sum of its proper divisors (1).

639686423 is an equidigital number, since it uses as much as digits as its factorization.

639686423 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1119744, while the sum is 47.

The square root of 639686423 is about 25292.0229123730. The cubic root of 639686423 is about 861.6331069432.

The spelling of 639686423 in words is "six hundred thirty-nine million, six hundred eighty-six thousand, four hundred twenty-three".