170221721 has 2 divisors, whose sum is σ = 170221722. Its totient is φ = 170221720.

The previous prime is 170221717. The next prime is 170221787. The reversal of 170221721 is 127122071.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 87684496 + 82537225 = 9364^2 + 9085^2 .

It is a cyclic number.

It is not a de Polignac number, because 170221721 - 2² = 170221717 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (170223721) 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 as a sum of consecutive naturals, namely, 85110860 + 85110861.

It is an arithmetic number, because the mean of its divisors is an integer number (85110861).

Almost surely, 2^170221721 is an apocalyptic number.

It is an amenable number.

170221721 is a deficient number, since it is larger than the sum of its proper divisors (1).

170221721 is an equidigital number, since it uses as much as digits as its factorization.

170221721 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 392, while the sum is 23.

The square root of 170221721 is about 13046.9046520621. The cubic root of 170221721 is about 554.2065560623.

Adding to 170221721 its reverse (127122071), we get a palindrome (297343792).

The spelling of 170221721 in words is "one hundred seventy million, two hundred twenty-one thousand, seven hundred twenty-one".