639902691 has 12 divisors (see below), whose sum is σ = 972951720. Its totient is φ = 404148960.

The previous prime is 639902671. The next prime is 639902699. The reversal of 639902691 is 196209936.

It is a happy number.

639902691 is a `hidden beast` number, since 639 + 9 + 0 + 2 + 6 + 9 + 1 = 666.

It is not a de Polignac number, because 639902691 - 2¹⁰ = 639901667 is a prime.

It is a super-3 number, since 3×639902691³ (a number of 27 digits) contains 333 as substring.

It is not an unprimeable number, because it can be changed into a prime (639902699) 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 in 11 ways as a sum of consecutive naturals, for example, 1870890 + ... + 1871231.

It is an arithmetic number, because the mean of its divisors is an integer number (81079310).

Almost surely, 2^639902691 is an apocalyptic number.

639902691 is a deficient number, since it is larger than the sum of its proper divisors (333049029).

639902691 is a wasteful number, since it uses less digits than its factorization.

639902691 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3742146 (or 3742143 counting only the distinct ones).

The product of its (nonzero) digits is 157464, while the sum is 45.

The square root of 639902691 is about 25296.2979702564. The cubic root of 639902691 is about 861.7301975729.

The spelling of 639902691 in words is "six hundred thirty-nine million, nine hundred two thousand, six hundred ninety-one".