638985221 has 4 divisors (see below), whose sum is σ = 730268832. Its totient is φ = 547701612.

The previous prime is 638985197. The next prime is 638985223. The reversal of 638985221 is 122589836.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 638985221 - 2¹⁸ = 638723077 is a prime.

It is a super-2 number, since 2×638985221² = 816604225312837682, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (638985223) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 45641795 + ... + 45641808.

It is an arithmetic number, because the mean of its divisors is an integer number (182567208).

Almost surely, 2^638985221 is an apocalyptic number.

It is an amenable number.

638985221 is a deficient number, since it is larger than the sum of its proper divisors (91283611).

638985221 is an equidigital number, since it uses as much as digits as its factorization.

638985221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 91283610.

The product of its digits is 207360, while the sum is 44.

The square root of 638985221 is about 25278.1569937367. The cubic root of 638985221 is about 861.3181610934.

The spelling of 638985221 in words is "six hundred thirty-eight million, nine hundred eighty-five thousand, two hundred twenty-one".