1721521 has 2 divisors, whose sum is σ = 1721522. Its totient is φ = 1721520.

The previous prime is 1721513. The next prime is 1721543. The reversal of 1721521 is 1251271.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1703025 + 18496 = 1305^2 + 136^2 .

It is a cyclic number.

It is not a de Polignac number, because 1721521 - 2³ = 1721513 is a prime.

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, 860760 + 860761.

It is an arithmetic number, because the mean of its divisors is an integer number (860761).

2^1721521 is an apocalyptic number.

It is an amenable number.

1721521 is a deficient number, since it is larger than the sum of its proper divisors (1).

1721521 is an equidigital number, since it uses as much as digits as its factorization.

1721521 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 140, while the sum is 19.

The square root of 1721521 is about 1312.0674525344. The cubic root of 1721521 is about 119.8498353146.

Adding to 1721521 its reverse (1251271), we get a palindrome (2972792).

The spelling of 1721521 in words is "one million, seven hundred twenty-one thousand, five hundred twenty-one".