221491 has 4 divisors (see below), whose sum is σ = 225184. Its totient is φ = 217800.

The previous prime is 221489. The next prime is 221497. The reversal of 221491 is 194122.

221491 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 a cyclic number.

It is not a de Polignac number, because 221491 - 2¹ = 221489 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (221497) 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, 1755 + ... + 1876.

It is an arithmetic number, because the mean of its divisors is an integer number (56296).

2²²¹⁴⁹¹ is an apocalyptic number.

221491 is a deficient number, since it is larger than the sum of its proper divisors (3693).

221491 is an equidigital number, since it uses as much as digits as its factorization.

221491 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3692.

The product of its digits is 144, while the sum is 19.

The square root of 221491 is about 470.6283034413. The cubic root of 221491 is about 60.5041774772.

The spelling of 221491 in words is "two hundred twenty-one thousand, four hundred ninety-one".