638221 has 4 divisors (see below), whose sum is σ = 640000. Its totient is φ = 636444.

The previous prime is 638201. The next prime is 638233. The reversal of 638221 is 122836.

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 638221 - 2⁹ = 637709 is a prime.

It is an Ulam number.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 638192 and 638201.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (638201) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 141 + ... + 1138.

It is an arithmetic number, because the mean of its divisors is an integer number (160000).

2⁶³⁸²²¹ is an apocalyptic number.

It is an amenable number.

638221 is a deficient number, since it is larger than the sum of its proper divisors (1779).

638221 is a wasteful number, since it uses less digits than its factorization.

638221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1778.

The product of its digits is 576, while the sum is 22.

The square root of 638221 is about 798.8873512580. The cubic root of 638221 is about 86.0974647663.

The spelling of 638221 in words is "six hundred thirty-eight thousand, two hundred twenty-one".