639693691 has 16 divisors (see below), whose sum is σ = 828755200. Its totient is φ = 479491488.

The previous prime is 639693683. The next prime is 639693713. The reversal of 639693691 is 196396936.

It is not a de Polignac number, because 639693691 - 2³ = 639693683 is a prime.

It is not an unprimeable number, because it can be changed into a prime (639693601) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 183261 + ... + 186718.

It is an arithmetic number, because the mean of its divisors is an integer number (51797200).

Almost surely, 2^639693691 is an apocalyptic number.

639693691 is a deficient number, since it is larger than the sum of its proper divisors (189061509).

639693691 is a wasteful number, since it uses less digits than its factorization.

639693691 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 370018.

The product of its digits is 1417176, while the sum is 52.

The square root of 639693691 is about 25292.1665936313. The cubic root of 639693691 is about 861.6363701701.

The spelling of 639693691 in words is "six hundred thirty-nine million, six hundred ninety-three thousand, six hundred ninety-one".