638661618556 has 24 divisors (see below), whose sum is σ = 1205251546464. Its totient is φ = 294370157760.

The previous prime is 638661618547. The next prime is 638661618589. The reversal of 638661618556 is 655816166836.

It is a junction number, because it is equal to n+sod(n) for n = 638661618494 and 638661618503.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 8226475 + ... + 8303746.

It is an arithmetic number, because the mean of its divisors is an integer number (50218814436).

Almost surely, 2^638661618556 is an apocalyptic number.

It is an amenable number.

638661618556 is a deficient number, since it is larger than the sum of its proper divisors (566589927908).

638661618556 is a wasteful number, since it uses less digits than its factorization.

638661618556 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16530981 (or 16530979 counting only the distinct ones).

The product of its digits is 37324800, while the sum is 61.

The spelling of 638661618556 in words is "six hundred thirty-eight billion, six hundred sixty-one million, six hundred eighteen thousand, five hundred fifty-six".