997 has 2 divisors, whose sum is σ = 998.
Its totient is φ = 996.
The previous prime is 991. The next prime is 1009. The reversal of 997 is 799.
It is a weak prime.
It can be written as a sum of positive squares in only one way, i.e., 961 + 36 = 31^2 + 6^2
997 is a truncatable prime.
It is a cyclic number.
It is a de Polignac number, because none of the positive numbers 2k-997 is a prime.
997 is a Gilda number.
997 is a lucky number.
It is a plaindrome in base 15.
It is a nialpdrome in base 4 and base 10.
It is a congruent number.
It is not a weakly prime, because it can be changed into another prime (991) by changing a digit.
It is a pernicious number, because its binary representation contains a prime number (7) of ones.
It is a polite number, since it can be written as a sum of consecutive naturals, namely, 498 + 499.
It is an arithmetic number, because the mean of its divisors is an integer number (499).
It is an amenable number.
997 is a deficient number, since it is larger than the sum of its proper divisors (1).
997 is an equidigital number, since it uses as much as digits as its factorization.
997 is an odious number, because the sum of its binary digits is odd.
The product of its digits is 567, while the sum is 25.
The square root of 997 is about 31.5753068077.
The cubic root of 997 is about 9.9899899833.
The spelling of 997 in words is "nine hundred ninety-seven", and is thus an aban number and an oban number.