1720581221 has 2 divisors, whose sum is σ = 1720581222. Its totient is φ = 1720581220.

The previous prime is 1720581199. The next prime is 1720581229. The reversal of 1720581221 is 1221850271.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1069617025 + 650964196 = 32705^2 + 25514^2 .

It is a cyclic number.

It is not a de Polignac number, because 1720581221 - 2¹⁸ = 1720319077 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1720581229) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 860290610 + 860290611.

It is an arithmetic number, because the mean of its divisors is an integer number (860290611).

Almost surely, 2^1720581221 is an apocalyptic number.

It is an amenable number.

1720581221 is a deficient number, since it is larger than the sum of its proper divisors (1).

1720581221 is an equidigital number, since it uses as much as digits as its factorization.

1720581221 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2240, while the sum is 29.

The square root of 1720581221 is about 41479.8893561687. The cubic root of 1720581221 is about 1198.2802265398.

The spelling of 1720581221 in words is "one billion, seven hundred twenty million, five hundred eighty-one thousand, two hundred twenty-one".