991897 has 4 divisors (see below), whose sum is σ = 995380. Its totient is φ = 988416.

The previous prime is 991889. The next prime is 991901. The reversal of 991897 is 798199.

991897 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 326041 + 665856 = 571^2 + 816^2 .

It is a cyclic number.

It is not a de Polignac number, because 991897 - 2³ = 991889 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (991817) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1272 + ... + 1897.

It is an arithmetic number, because the mean of its divisors is an integer number (248845).

2⁹⁹¹⁸⁹⁷ is an apocalyptic number.

It is an amenable number.

991897 is a deficient number, since it is larger than the sum of its proper divisors (3483).

991897 is a wasteful number, since it uses less digits than its factorization.

991897 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3482.

The product of its digits is 40824, while the sum is 43.

The square root of 991897 is about 995.9402592525. The cubic root of 991897 is about 99.7291671579.

The spelling of 991897 in words is "nine hundred ninety-one thousand, eight hundred ninety-seven".