1720220221 has 2 divisors, whose sum is σ = 1720220222. Its totient is φ = 1720220220.

The previous prime is 1720220171. The next prime is 1720220321. The reversal of 1720220221 is 1220220271.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1156680100 + 563540121 = 34010^2 + 23739^2 .

It is a cyclic number.

It is not a de Polignac number, because 1720220221 - 2¹⁹ = 1719695933 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1720220321) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 860110110 + 860110111.

It is an arithmetic number, because the mean of its divisors is an integer number (860110111).

Almost surely, 2^1720220221 is an apocalyptic number.

It is an amenable number.

1720220221 is a deficient number, since it is larger than the sum of its proper divisors (1).

1720220221 is an equidigital number, since it uses as much as digits as its factorization.

1720220221 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 224, while the sum is 19.

The square root of 1720220221 is about 41475.5376215909. The cubic root of 1720220221 is about 1198.1964158263.

Adding to 1720220221 its reverse (1220220271), we get a palindrome (2940440492).

The spelling of 1720220221 in words is "one billion, seven hundred twenty million, two hundred twenty thousand, two hundred twenty-one".