991873 has 2 divisors, whose sum is σ = 991874. Its totient is φ = 991872.

The previous prime is 991871. The next prime is 991883. The reversal of 991873 is 378199.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 944784 + 47089 = 972^2 + 217^2 .

It is a cyclic number.

It is not a de Polignac number, because 991873 - 2¹ = 991871 is a prime.

Together with 991871, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (991871) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 495936 + 495937.

It is an arithmetic number, because the mean of its divisors is an integer number (495937).

2⁹⁹¹⁸⁷³ is an apocalyptic number.

It is an amenable number.

991873 is a deficient number, since it is larger than the sum of its proper divisors (1).

991873 is an equidigital number, since it uses as much as digits as its factorization.

991873 is an evil number, because the sum of its binary digits is even.

The product of its digits is 13608, while the sum is 37.

The square root of 991873 is about 995.9282102642. The cubic root of 991873 is about 99.7283628004.

The spelling of 991873 in words is "nine hundred ninety-one thousand, eight hundred seventy-three".