991215 has 12 divisors (see below), whose sum is σ = 1718184. Its totient is φ = 528624.

The previous prime is 991201. The next prime is 991217. The reversal of 991215 is 512199.

It is a happy number.

It is not a de Polignac number, because 991215 - 2¹⁶ = 925679 is a prime.

991215 is a lucky number.

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 11 ways as a sum of consecutive naturals, for example, 10969 + ... + 11058.

It is an arithmetic number, because the mean of its divisors is an integer number (143182).

2⁹⁹¹²¹⁵ is an apocalyptic number.

991215 is a deficient number, since it is larger than the sum of its proper divisors (726969).

991215 is a wasteful number, since it uses less digits than its factorization.

991215 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 22038 (or 22035 counting only the distinct ones).

The product of its digits is 810, while the sum is 27.

The square root of 991215 is about 995.5978103632. The cubic root of 991215 is about 99.7063049432.

The spelling of 991215 in words is "nine hundred ninety-one thousand, two hundred fifteen".