1721321 has 6 divisors (see below), whose sum is σ = 2002410. Its totient is φ = 1475376.

The previous prime is 1721299. The next prime is 1721323. The reversal of 1721321 is 1231271.

It can be written as a sum of positive squares in only one way, i.e., 1073296 + 648025 = 1036^2 + 805^2 .

It is not a de Polignac number, because 1721321 - 2⁶ = 1721257 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 1721321.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1721323) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 17516 + ... + 17613.

It is an arithmetic number, because the mean of its divisors is an integer number (333735).

2^1721321 is an apocalyptic number.

It is an amenable number.

1721321 is a deficient number, since it is larger than the sum of its proper divisors (281089).

1721321 is an equidigital number, since it uses as much as digits as its factorization.

1721321 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 35143 (or 35136 counting only the distinct ones).

The product of its digits is 84, while the sum is 17.

The square root of 1721321 is about 1311.9912347268. The cubic root of 1721321 is about 119.8451938966.

Adding to 1721321 its reverse (1231271), we get a palindrome (2952592).

The spelling of 1721321 in words is "one million, seven hundred twenty-one thousand, three hundred twenty-one".