638293221 has 6 divisors (see below), whose sum is σ = 921979110. Its totient is φ = 425528808.

The previous prime is 638293213. The next prime is 638293223. The reversal of 638293221 is 122392836.

It can be written as a sum of positive squares in only one way, i.e., 511392996 + 126900225 = 22614^2 + 11265^2 .

It is not a de Polignac number, because 638293221 - 2³ = 638293213 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (638293223) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 35460726 + ... + 35460743.

It is an arithmetic number, because the mean of its divisors is an integer number (153663185).

Almost surely, 2^638293221 is an apocalyptic number.

It is an amenable number.

638293221 is a deficient number, since it is larger than the sum of its proper divisors (283685889).

638293221 is a wasteful number, since it uses less digits than its factorization.

638293221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 70921475 (or 70921472 counting only the distinct ones).

The product of its digits is 31104, while the sum is 36.

The square root of 638293221 is about 25264.4655791489. The cubic root of 638293221 is about 861.0071223617.

The spelling of 638293221 in words is "six hundred thirty-eight million, two hundred ninety-three thousand, two hundred twenty-one".