1720561 has 8 divisors (see below), whose sum is σ = 1808640. Its totient is φ = 1633632.

The previous prime is 1720549. The next prime is 1720591. The reversal of 1720561 is 1650271.

It is the 536-th star number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 1720561 - 2⁹ = 1720049 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1720591) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 5341 + ... + 5653.

It is an arithmetic number, because the mean of its divisors is an integer number (226080).

2^1720561 is an apocalyptic number.

It is an amenable number.

1720561 is a deficient number, since it is larger than the sum of its proper divisors (88079).

1720561 is a wasteful number, since it uses less digits than its factorization.

1720561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 575.

The product of its (nonzero) digits is 420, while the sum is 22.

The square root of 1720561 is about 1311.7015666683. The cubic root of 1720561 is about 119.8275532289.

The spelling of 1720561 in words is "one million, seven hundred twenty thousand, five hundred sixty-one".