991957 has 2 divisors, whose sum is σ = 991958. Its totient is φ = 991956.

The previous prime is 991951. The next prime is 991961. The reversal of 991957 is 759199.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 799236 + 192721 = 894^2 + 439^2 .

It is a cyclic number.

It is not a de Polignac number, because 991957 - 2¹¹ = 989909 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (991951) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 495978 + 495979.

It is an arithmetic number, because the mean of its divisors is an integer number (495979).

2⁹⁹¹⁹⁵⁷ is an apocalyptic number.

It is an amenable number.

991957 is a deficient number, since it is larger than the sum of its proper divisors (1).

991957 is an equidigital number, since it uses as much as digits as its factorization.

991957 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 25515, while the sum is 40.

The square root of 991957 is about 995.9703810857. The cubic root of 991957 is about 99.7311779948.

The spelling of 991957 in words is "nine hundred ninety-one thousand, nine hundred fifty-seven".