991287 has 48 divisors (see below), whose sum is σ = 1797120. Its totient is φ = 518400.

The previous prime is 991273. The next prime is 991313. The reversal of 991287 is 782199.

It is a happy number.

991287 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 991287 - 2⁶ = 991223 is a prime.

Its product of digits (9072) is a multiple of the sum of its prime divisors (81).

It is a plaindrome in base 15.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (991217) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 31962 + ... + 31992.

It is an arithmetic number, because the mean of its divisors is an integer number (37440).

2⁹⁹¹²⁸⁷ is an apocalyptic number.

991287 is a deficient number, since it is larger than the sum of its proper divisors (805833).

991287 is a wasteful number, since it uses less digits than its factorization.

991287 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 84 (or 81 counting only the distinct ones).

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

The square root of 991287 is about 995.6339688862. The cubic root of 991287 is about 99.7087190445.

It can be divided in two parts, 9912 and 87, that added together give a palindrome (9999).

The spelling of 991287 in words is "nine hundred ninety-one thousand, two hundred eighty-seven".