221981 has 4 divisors (see below), whose sum is σ = 226752. Its totient is φ = 217212.

The previous prime is 221957. The next prime is 221987. The reversal of 221981 is 189122.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 189122 = 2 ⋅94561.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-221981 is a prime.

It is a super-2 number, since 2×221981² = 98551128722, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (221987) 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, 2315 + ... + 2408.

It is an arithmetic number, because the mean of its divisors is an integer number (56688).

2²²¹⁹⁸¹ is an apocalyptic number.

It is an amenable number.

221981 is a deficient number, since it is larger than the sum of its proper divisors (4771).

221981 is an equidigital number, since it uses as much as digits as its factorization.

221981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4770.

The product of its digits is 288, while the sum is 23.

The square root of 221981 is about 471.1485965171. The cubic root of 221981 is about 60.5487619995.

The spelling of 221981 in words is "two hundred twenty-one thousand, nine hundred eighty-one".