991751 has 2 divisors, whose sum is σ = 991752. Its totient is φ = 991750.

The previous prime is 991741. The next prime is 991777. The reversal of 991751 is 157199.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 991751 - 2¹⁴ = 975367 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is an Ulam number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (991741) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 495875 + 495876.

It is an arithmetic number, because the mean of its divisors is an integer number (495876).

2⁹⁹¹⁷⁵¹ is an apocalyptic number.

991751 is a deficient number, since it is larger than the sum of its proper divisors (1).

991751 is an equidigital number, since it uses as much as digits as its factorization.

991751 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2835, while the sum is 32.

The square root of 991751 is about 995.8669589860. The cubic root of 991751 is about 99.7242737826.

The spelling of 991751 in words is "nine hundred ninety-one thousand, seven hundred fifty-one".