1721509 has 2 divisors, whose sum is σ = 1721510. Its totient is φ = 1721508.

The previous prime is 1721507. The next prime is 1721513. The reversal of 1721509 is 9051271.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 950625 + 770884 = 975^2 + 878^2 .

It is a cyclic number.

It is not a de Polignac number, because 1721509 - 2¹ = 1721507 is a prime.

Together with 1721507, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1721501) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 860754 + 860755.

It is an arithmetic number, because the mean of its divisors is an integer number (860755).

2^1721509 is an apocalyptic number.

It is an amenable number.

1721509 is a deficient number, since it is larger than the sum of its proper divisors (1).

1721509 is an equidigital number, since it uses as much as digits as its factorization.

1721509 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 630, while the sum is 25.

The square root of 1721509 is about 1312.0628795908. The cubic root of 1721509 is about 119.8495568397.

It can be divided in two parts, 172 and 1509, that added together give a square (1681 = 41²).

The spelling of 1721509 in words is "one million, seven hundred twenty-one thousand, five hundred nine".