321721649 has 2 divisors, whose sum is σ = 321721650. Its totient is φ = 321721648.

The previous prime is 321721643. The next prime is 321721669. The reversal of 321721649 is 946127123.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 251698225 + 70023424 = 15865^2 + 8368^2 .

It is an emirp because it is prime and its reverse (946127123) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-321721649 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (321721643) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 160860824 + 160860825.

It is an arithmetic number, because the mean of its divisors is an integer number (160860825).

Almost surely, 2^321721649 is an apocalyptic number.

It is an amenable number.

321721649 is a deficient number, since it is larger than the sum of its proper divisors (1).

321721649 is an equidigital number, since it uses as much as digits as its factorization.

321721649 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 18144, while the sum is 35.

The square root of 321721649 is about 17936.6008206683. The cubic root of 321721649 is about 685.2148430116.

The spelling of 321721649 in words is "three hundred twenty-one million, seven hundred twenty-one thousand, six hundred forty-nine".