197991 has 8 divisors (see below), whose sum is σ = 293360. Its totient is φ = 131976.

The previous prime is 197971. The next prime is 198013. The reversal of 197991 is 199791.

197991 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 197991 - 2⁵ = 197959 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (197921) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3640 + ... + 3693.

It is an arithmetic number, because the mean of its divisors is an integer number (36670).

2¹⁹⁷⁹⁹¹ is an apocalyptic number.

197991 is a deficient number, since it is larger than the sum of its proper divisors (95369).

197991 is an equidigital number, since it uses as much as digits as its factorization.

197991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7342 (or 7336 counting only the distinct ones).

The product of its digits is 5103, while the sum is 36.

The square root of 197991 is about 444.9617961129. The cubic root of 197991 is about 58.2838837166.

The spelling of 197991 in words is "one hundred ninety-seven thousand, nine hundred ninety-one".