639346981 has 8 divisors (see below), whose sum is σ = 786888704. Its totient is φ = 505856880.

The previous prime is 639346957. The next prime is 639346993. The reversal of 639346981 is 189643936.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 639346981 - 2⁹ = 639346469 is a prime.

It is a super-2 number, since 2×639346981² = 817529124227628722, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (639346681) 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, 3512805 + ... + 3512986.

It is an arithmetic number, because the mean of its divisors is an integer number (98361088).

Almost surely, 2^639346981 is an apocalyptic number.

It is an amenable number.

639346981 is a deficient number, since it is larger than the sum of its proper divisors (147541723).

639346981 is a wasteful number, since it uses less digits than its factorization.

639346981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7025811.

The product of its digits is 839808, while the sum is 49.

The square root of 639346981 is about 25285.3115662038. The cubic root of 639346981 is about 861.4806748544.

The spelling of 639346981 in words is "six hundred thirty-nine million, three hundred forty-six thousand, nine hundred eighty-one".