221945 has 4 divisors (see below), whose sum is σ = 266340. Its totient is φ = 177552.

The previous prime is 221941. The next prime is 221951. The reversal of 221945 is 549122.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 162409 + 59536 = 403^2 + 244^2 .

It is a cyclic number.

It is not a de Polignac number, because 221945 - 2² = 221941 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 221945.

It is not an unprimeable number, because it can be changed into a prime (221941) 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, 22190 + ... + 22199.

It is an arithmetic number, because the mean of its divisors is an integer number (66585).

2²²¹⁹⁴⁵ is an apocalyptic number.

It is an amenable number.

221945 is a deficient number, since it is larger than the sum of its proper divisors (44395).

221945 is an equidigital number, since it uses as much as digits as its factorization.

221945 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 44394.

The product of its digits is 720, while the sum is 23.

The square root of 221945 is about 471.1103904607. The cubic root of 221945 is about 60.5454886363.

The spelling of 221945 in words is "two hundred twenty-one thousand, nine hundred forty-five".