639697840 has 40 divisors (see below), whose sum is σ = 1493565120. Its totient is φ = 254800896.

The previous prime is 639697837. The next prime is 639697841. The reversal of 639697840 is 48796936.

It is a tau number, because it is divible by the number of its divisors (40).

It is not an unprimeable number, because it can be changed into a prime (639697841) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2392 + ... + 35848.

It is an arithmetic number, because the mean of its divisors is an integer number (37339128).

Almost surely, 2^639697840 is an apocalyptic number.

It is an amenable number.

639697840 is an abundant number, since it is smaller than the sum of its proper divisors (853867280).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

639697840 is a wasteful number, since it uses less digits than its factorization.

639697840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 33709 (or 33703 counting only the distinct ones).

The product of its (nonzero) digits is 1959552, while the sum is 52.

The square root of 639697840 is about 25292.2486149413. The cubic root of 639697840 is about 861.6382330000.

The spelling of 639697840 in words is "six hundred thirty-nine million, six hundred ninety-seven thousand, eight hundred forty".