221791 has 4 divisors (see below), whose sum is σ = 222912. Its totient is φ = 220672.

The previous prime is 221773. The next prime is 221797. The reversal of 221791 is 197122.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 197122 = 2 ⋅98561.

It is a cyclic number.

It is not a de Polignac number, because 221791 - 2¹³ = 213599 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 (221797) 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, 175 + ... + 688.

It is an arithmetic number, because the mean of its divisors is an integer number (55728).

2²²¹⁷⁹¹ is an apocalyptic number.

221791 is a deficient number, since it is larger than the sum of its proper divisors (1121).

221791 is an equidigital number, since it uses as much as digits as its factorization.

221791 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1120.

The product of its digits is 252, while the sum is 22.

The square root of 221791 is about 470.9469184526. The cubic root of 221791 is about 60.5314819190.

The spelling of 221791 in words is "two hundred twenty-one thousand, seven hundred ninety-one".