971991 has 6 divisors (see below), whose sum is σ = 1404000. Its totient is φ = 647988.

The previous prime is 971989. The next prime is 972001. The reversal of 971991 is 199179.

It is not a de Polignac number, because 971991 - 2¹ = 971989 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (971921) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 53991 + ... + 54008.

It is an arithmetic number, because the mean of its divisors is an integer number (234000).

2⁹⁷¹⁹⁹¹ is an apocalyptic number.

971991 is a deficient number, since it is larger than the sum of its proper divisors (432009).

971991 is a wasteful number, since it uses less digits than its factorization.

971991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 108005 (or 108002 counting only the distinct ones).

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

The square root of 971991 is about 985.8960391441. The cubic root of 971991 is about 99.0575117319.

The spelling of 971991 in words is "nine hundred seventy-one thousand, nine hundred ninety-one".