321105991 has 2 divisors, whose sum is σ = 321105992. Its totient is φ = 321105990.

The previous prime is 321105989. The next prime is 321106031. The reversal of 321105991 is 199501123.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 321105991 - 2¹ = 321105989 is a prime.

Together with 321105989, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (321105971) 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, 160552995 + 160552996.

It is an arithmetic number, because the mean of its divisors is an integer number (160552996).

Almost surely, 2^321105991 is an apocalyptic number.

321105991 is a deficient number, since it is larger than the sum of its proper divisors (1).

321105991 is an equidigital number, since it uses as much as digits as its factorization.

321105991 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2430, while the sum is 31.

The square root of 321105991 is about 17919.4305434073. The cubic root of 321105991 is about 684.7774800699. Note that the first 3 decimals are identical.

The spelling of 321105991 in words is "three hundred twenty-one million, one hundred five thousand, nine hundred ninety-one".