991878 has 8 divisors (see below), whose sum is σ = 1983768. Its totient is φ = 330624.

The previous prime is 991873. The next prime is 991883. The reversal of 991878 is 878199.

It is an interprime number because it is at equal distance from previous prime (991873) and next prime (991883).

It is a sphenic number, since it is the product of 3 distinct primes.

991878 is an admirable number.

It is an Ulam number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (991871) 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, 82651 + ... + 82662.

It is an arithmetic number, because the mean of its divisors is an integer number (247971).

2⁹⁹¹⁸⁷⁸ is an apocalyptic number.

991878 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

991878 is a wasteful number, since it uses less digits than its factorization.

991878 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 165318.

The product of its digits is 36288, while the sum is 42.

The square root of 991878 is about 995.9307204821. The cubic root of 991878 is about 99.7285303760.

The spelling of 991878 in words is "nine hundred ninety-one thousand, eight hundred seventy-eight".