1721569 has 2 divisors, whose sum is σ = 1721570. Its totient is φ = 1721568.

The previous prime is 1721567. The next prime is 1721579. The reversal of 1721569 is 9651271.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1721344 + 225 = 1312^2 + 15^2 .

It is a cyclic number.

It is not a de Polignac number, because 1721569 - 2¹ = 1721567 is a prime.

It is a super-2 number, since 2×1721569² = 5927599643522, which contains 22 as substring.

Together with 1721567, it forms a pair of twin primes.

It is a self number, because there is not a number n which added to its sum of digits gives 1721569.

It is not a weakly prime, because it can be changed into another prime (1721567) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 860784 + 860785.

It is an arithmetic number, because the mean of its divisors is an integer number (860785).

2^1721569 is an apocalyptic number.

It is an amenable number.

1721569 is a deficient number, since it is larger than the sum of its proper divisors (1).

1721569 is an equidigital number, since it uses as much as digits as its factorization.

1721569 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 3780, while the sum is 31.

The square root of 1721569 is about 1312.0857441494. The cubic root of 1721569 is about 119.8509492014.

The spelling of 1721569 in words is "one million, seven hundred twenty-one thousand, five hundred sixty-nine".