321691621 has 2 divisors, whose sum is σ = 321691622. Its totient is φ = 321691620.

The previous prime is 321691607. The next prime is 321691631. The reversal of 321691621 is 126196123.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 320768100 + 923521 = 17910^2 + 961^2 .

It is a cyclic number.

It is not a de Polignac number, because 321691621 - 2¹⁷ = 321560549 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (321691631) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 160845810 + 160845811.

It is an arithmetic number, because the mean of its divisors is an integer number (160845811).

Almost surely, 2^321691621 is an apocalyptic number.

It is an amenable number.

321691621 is a deficient number, since it is larger than the sum of its proper divisors (1).

321691621 is an equidigital number, since it uses as much as digits as its factorization.

321691621 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 3888, while the sum is 31.

The square root of 321691621 is about 17935.7637417535. The cubic root of 321691621 is about 685.1935240945.

The spelling of 321691621 in words is "three hundred twenty-one million, six hundred ninety-one thousand, six hundred twenty-one".