221021173 has 2 divisors, whose sum is σ = 221021174. Its totient is φ = 221021172.

The previous prime is 221021159. The next prime is 221021179. The reversal of 221021173 is 371120122.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 220879044 + 142129 = 14862^2 + 377^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-221021173 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 221021173.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (221021179) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 110510586 + 110510587.

It is an arithmetic number, because the mean of its divisors is an integer number (110510587).

Almost surely, 2^221021173 is an apocalyptic number.

It is an amenable number.

221021173 is a deficient number, since it is larger than the sum of its proper divisors (1).

221021173 is an equidigital number, since it uses as much as digits as its factorization.

221021173 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 168, while the sum is 19.

The square root of 221021173 is about 14866.7808553163. The cubic root of 221021173 is about 604.6136667922.

Adding to 221021173 its reverse (371120122), we get a palindrome (592141295).

The spelling of 221021173 in words is "two hundred twenty-one million, twenty-one thousand, one hundred seventy-three".