639768645 has 16 divisors (see below), whose sum is σ = 1137366720. Its totient is φ = 341209872.

The previous prime is 639768617. The next prime is 639768673. The reversal of 639768645 is 546867936.

It is an interprime number because it is at equal distance from previous prime (639768617) and next prime (639768673).

It is not a de Polignac number, because 639768645 - 2¹² = 639764549 is a prime.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 639768591 and 639768600.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2369379 + ... + 2369648.

It is an arithmetic number, because the mean of its divisors is an integer number (71085420).

Almost surely, 2^639768645 is an apocalyptic number.

It is an amenable number.

639768645 is a deficient number, since it is larger than the sum of its proper divisors (497598075).

639768645 is a wasteful number, since it uses less digits than its factorization.

639768645 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4739041 (or 4739035 counting only the distinct ones).

The product of its digits is 6531840, while the sum is 54.

The square root of 639768645 is about 25293.6483133612. The cubic root of 639768645 is about 861.6700219898.

The spelling of 639768645 in words is "six hundred thirty-nine million, seven hundred sixty-eight thousand, six hundred forty-five".