638661256 has 16 divisors (see below), whose sum is σ = 1236119040. Its totient is φ = 309029520.

The previous prime is 638661211. The next prime is 638661281. The reversal of 638661256 is 652166836.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1287376 + ... + 1287871.

It is an arithmetic number, because the mean of its divisors is an integer number (77257440).

Almost surely, 2^638661256 is an apocalyptic number.

It is an amenable number.

638661256 is a deficient number, since it is larger than the sum of its proper divisors (597457784).

638661256 is a wasteful number, since it uses less digits than its factorization.

638661256 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2575284 (or 2575280 counting only the distinct ones).

The product of its digits is 311040, while the sum is 43.

The square root of 638661256 is about 25271.7481785491. The cubic root of 638661256 is about 861.1725739451.

The spelling of 638661256 in words is "six hundred thirty-eight million, six hundred sixty-one thousand, two hundred fifty-six".