991278 has 40 divisors (see below), whose sum is σ = 2308680. Its totient is φ = 317520.

The previous prime is 991273. The next prime is 991313. The reversal of 991278 is 872199.

It is a happy number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (991273) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 4593 + ... + 4803.

It is an arithmetic number, because the mean of its divisors is an integer number (57717).

2⁹⁹¹²⁷⁸ is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 991278, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1154340).

991278 is an abundant number, since it is smaller than the sum of its proper divisors (1317402).

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

991278 is a wasteful number, since it uses less digits than its factorization.

991278 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 254 (or 245 counting only the distinct ones).

The product of its digits is 9072, while the sum is 36.

The square root of 991278 is about 995.6294491426. The cubic root of 991278 is about 99.7084172882.

The spelling of 991278 in words is "nine hundred ninety-one thousand, two hundred seventy-eight".