991858 has 24 divisors (see below), whose sum is σ = 1795500. Its totient is φ = 409248.

The previous prime is 991817. The next prime is 991867. The reversal of 991858 is 858199.

991858 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in 2 ways, for example, as 974169 + 17689 = 987^2 + 133^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 991858.

It is an unprimeable number.

991858 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 2668 + ... + 3016.

2⁹⁹¹⁸⁵⁸ is an apocalyptic number.

991858 is a gapful number since it is divisible by the number (98) formed by its first and last digit.

991858 is a deficient number, since it is larger than the sum of its proper divisors (803642).

991858 is a wasteful number, since it uses less digits than its factorization.

991858 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 394 (or 387 counting only the distinct ones).

The product of its digits is 25920, while the sum is 40.

The square root of 991858 is about 995.9206795724. The cubic root of 991858 is about 99.7278600704.

It can be divided in two parts, 991 and 858, that added together give a square (1849 = 43²).

The spelling of 991858 in words is "nine hundred ninety-one thousand, eight hundred fifty-eight".