401197991 has 2 divisors, whose sum is σ = 401197992. Its totient is φ = 401197990.

The previous prime is 401197987. The next prime is 401198009. The reversal of 401197991 is 199791104.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 401197991 - 2² = 401197987 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (401197591) 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, 200598995 + 200598996.

It is an arithmetic number, because the mean of its divisors is an integer number (200598996).

Almost surely, 2^401197991 is an apocalyptic number.

401197991 is a deficient number, since it is larger than the sum of its proper divisors (1).

401197991 is an equidigital number, since it uses as much as digits as its factorization.

401197991 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 20412, while the sum is 41.

The square root of 401197991 is about 20029.9273837925. The cubic root of 401197991 is about 737.5411393694.

The spelling of 401197991 in words is "four hundred one million, one hundred ninety-seven thousand, nine hundred ninety-one".