320561001991 has 2 divisors, whose sum is σ = 320561001992. Its totient is φ = 320561001990.

The previous prime is 320561001967. The next prime is 320561002031. The reversal of 320561001991 is 199100165023.

It is a happy number.

It is a weak prime.

It is an emirp because it is prime and its reverse (199100165023) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 320561001991 - 2²⁷ = 320426784263 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 320561001991.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (320561005991) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 160280500995 + 160280500996.

It is an arithmetic number, because the mean of its divisors is an integer number (160280500996).

Almost surely, 2^320561001991 is an apocalyptic number.

320561001991 is a deficient number, since it is larger than the sum of its proper divisors (1).

320561001991 is an equidigital number, since it uses as much as digits as its factorization.

320561001991 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 14580, while the sum is 37.

The spelling of 320561001991 in words is "three hundred twenty billion, five hundred sixty-one million, one thousand, nine hundred ninety-one".