1720399 has 2 divisors, whose sum is σ = 1720400. Its totient is φ = 1720398.

The previous prime is 1720379. The next prime is 1720421. The reversal of 1720399 is 9930271.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 1720399 - 2¹⁷ = 1589327 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 1720399.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1720339) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 860199 + 860200.

It is an arithmetic number, because the mean of its divisors is an integer number (860200).

2^1720399 is an apocalyptic number.

1720399 is a deficient number, since it is larger than the sum of its proper divisors (1).

1720399 is an equidigital number, since it uses as much as digits as its factorization.

1720399 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 3402, while the sum is 31.

The square root of 1720399 is about 1311.6398133634. The cubic root of 1720399 is about 119.8237923097.

The spelling of 1720399 in words is "one million, seven hundred twenty thousand, three hundred ninety-nine".