1991409197 has 2 divisors, whose sum is σ = 1991409198. Its totient is φ = 1991409196.

The previous prime is 1991409193. The next prime is 1991409229. The reversal of 1991409197 is 7919041991.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1990141321 + 1267876 = 44611^2 + 1126^2 .

It is a cyclic number.

It is not a de Polignac number, because 1991409197 - 2² = 1991409193 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1991409191) 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, 995704598 + 995704599.

It is an arithmetic number, because the mean of its divisors is an integer number (995704599).

Almost surely, 2^1991409197 is an apocalyptic number.

It is an amenable number.

1991409197 is a deficient number, since it is larger than the sum of its proper divisors (1).

1991409197 is an equidigital number, since it uses as much as digits as its factorization.

1991409197 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 183708, while the sum is 50.

The square root of 1991409197 is about 44625.2080891507. The cubic root of 1991409197 is about 1258.1145052198.

The spelling of 1991409197 in words is "one billion, nine hundred ninety-one million, four hundred nine thousand, one hundred ninety-seven".