221581 has 2 divisors, whose sum is σ = 221582. Its totient is φ = 221580.

The previous prime is 221567. The next prime is 221587. The reversal of 221581 is 185122.

221581 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 136900 + 84681 = 370^2 + 291^2 .

It is a cyclic number.

It is not a de Polignac number, because 221581 - 2⁵ = 221549 is a prime.

It is a super-2 number, since 2×221581² = 98196279122, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (221587) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 110790 + 110791.

It is an arithmetic number, because the mean of its divisors is an integer number (110791).

2²²¹⁵⁸¹ is an apocalyptic number.

It is an amenable number.

221581 is a deficient number, since it is larger than the sum of its proper divisors (1).

221581 is an equidigital number, since it uses as much as digits as its factorization.

221581 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 160, while the sum is 19.

The square root of 221581 is about 470.7239105888. The cubic root of 221581 is about 60.5123713972.

The spelling of 221581 in words is "two hundred twenty-one thousand, five hundred eighty-one".