220991 has 4 divisors (see below), whose sum is σ = 221952. Its totient is φ = 220032.

The previous prime is 220973. The next prime is 221021. The reversal of 220991 is 199022.

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.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-220991 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 (220901) 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, 95 + ... + 671.

It is an arithmetic number, because the mean of its divisors is an integer number (55488).

2²²⁰⁹⁹¹ is an apocalyptic number.

220991 is a deficient number, since it is larger than the sum of its proper divisors (961).

220991 is an equidigital number, since it uses as much as digits as its factorization.

220991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 960.

The product of its (nonzero) digits is 324, while the sum is 23.

The square root of 220991 is about 470.0967985426. The cubic root of 220991 is about 60.4586152327.

The spelling of 220991 in words is "two hundred twenty thousand, nine hundred ninety-one".