221638 has 4 divisors (see below), whose sum is σ = 332460. Its totient is φ = 110818.

The previous prime is 221623. The next prime is 221653. The reversal of 221638 is 836122.

221638 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes.

It is an interprime number because it is at equal distance from previous prime (221623) and next prime (221653).

It is a Smith number, since the sum of its digits (22) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 55408 + ... + 55411.

It is an arithmetic number, because the mean of its divisors is an integer number (83115).

2²²¹⁶³⁸ is an apocalyptic number.

221638 is a deficient number, since it is larger than the sum of its proper divisors (110822).

221638 is a wasteful number, since it uses less digits than its factorization.

221638 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 110821.

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

The square root of 221638 is about 470.7844517399. The cubic root of 221638 is about 60.5175597323.

The spelling of 221638 in words is "two hundred twenty-one thousand, six hundred thirty-eight".