1720981321 has 2 divisors, whose sum is σ = 1720981322. Its totient is φ = 1720981320.

The previous prime is 1720981313. The next prime is 1720981331. The reversal of 1720981321 is 1231890271.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1262807296 + 458174025 = 35536^2 + 21405^2 .

It is an emirp because it is prime and its reverse (1231890271) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1720981321 - 2³ = 1720981313 is a prime.

It is not a weakly prime, because it can be changed into another prime (1720981331) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 860490660 + 860490661.

It is an arithmetic number, because the mean of its divisors is an integer number (860490661).

Almost surely, 2^1720981321 is an apocalyptic number.

It is an amenable number.

1720981321 is a deficient number, since it is larger than the sum of its proper divisors (1).

1720981321 is an equidigital number, since it uses as much as digits as its factorization.

1720981321 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 6048, while the sum is 34.

The square root of 1720981321 is about 41484.7118948656. The cubic root of 1720981321 is about 1198.3731011172.

The spelling of 1720981321 in words is "one billion, seven hundred twenty million, nine hundred eighty-one thousand, three hundred twenty-one".