321721 has 2 divisors, whose sum is σ = 321722. Its totient is φ = 321720.

The previous prime is 321709. The next prime is 321733. The reversal of 321721 is 127123.

It is a happy number.

321721 is nontrivially palindromic in base 2.

It is a balanced prime because it is at equal distance from previous prime (321709) and next prime (321733).

It can be written as a sum of positive squares in only one way, i.e., 189225 + 132496 = 435^2 + 364^2 .

It is an emirp because it is prime and its reverse (127123) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 321721 - 2⁷ = 321593 is a prime.

321721 is a lucky number.

It is a junction number, because it is equal to n+sod(n) for n = 321695 and 321704.

It is not a weakly prime, because it can be changed into another prime (321751) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 160860 + 160861.

It is an arithmetic number, because the mean of its divisors is an integer number (160861).

2³²¹⁷²¹ is an apocalyptic number.

It is an amenable number.

321721 is a deficient number, since it is larger than the sum of its proper divisors (1).

321721 is an equidigital number, since it uses as much as digits as its factorization.

321721 is an evil number, because the sum of its binary digits is even.

The product of its digits is 84, while the sum is 16.

The square root of 321721 is about 567.2045486418. The cubic root of 321721 is about 68.5214382256.

Adding to 321721 its reverse (127123), we get a palindrome (448844).

The spelling of 321721 in words is "three hundred twenty-one thousand, seven hundred twenty-one", and thus it is an iban number.