320421991 has 2 divisors, whose sum is σ = 320421992. Its totient is φ = 320421990.

The previous prime is 320421971. The next prime is 320422007. The reversal of 320421991 is 199124023.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 320421991 - 2⁷ = 320421863 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (320421931) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 160210995 + 160210996.

It is an arithmetic number, because the mean of its divisors is an integer number (160210996).

Almost surely, 2^320421991 is an apocalyptic number.

320421991 is a deficient number, since it is larger than the sum of its proper divisors (1).

320421991 is an equidigital number, since it uses as much as digits as its factorization.

320421991 is an evil number, because the sum of its binary digits is even.

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

The square root of 320421991 is about 17900.3349410004. The cubic root of 320421991 is about 684.2909109614.

The spelling of 320421991 in words is "three hundred twenty million, four hundred twenty-one thousand, nine hundred ninety-one".