221591 has 4 divisors (see below), whose sum is σ = 224784. Its totient is φ = 218400.

The previous prime is 221587. The next prime is 221603. The reversal of 221591 is 195122.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 195122 = 2 ⋅97561.

It is a cyclic number.

It is not a de Polignac number, because 221591 - 2² = 221587 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (221581) 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, 1490 + ... + 1631.

It is an arithmetic number, because the mean of its divisors is an integer number (56196).

2²²¹⁵⁹¹ is an apocalyptic number.

221591 is a deficient number, since it is larger than the sum of its proper divisors (3193).

221591 is an equidigital number, since it uses as much as digits as its factorization.

221591 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3192.

The product of its digits is 180, while the sum is 20.

The square root of 221591 is about 470.7345324065. The cubic root of 221591 is about 60.5132816957.

The spelling of 221591 in words is "two hundred twenty-one thousand, five hundred ninety-one".