991615 has 4 divisors (see below), whose sum is σ = 1189944. Its totient is φ = 793288.

The previous prime is 991607. The next prime is 991619. The reversal of 991615 is 516199.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 991615 - 2³ = 991607 is a prime.

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (991619) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 99157 + ... + 99166.

It is an arithmetic number, because the mean of its divisors is an integer number (297486).

2⁹⁹¹⁶¹⁵ is an apocalyptic number.

991615 is a deficient number, since it is larger than the sum of its proper divisors (198329).

991615 is a wasteful number, since it uses less digits than its factorization.

991615 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 198328.

The product of its digits is 2430, while the sum is 31.

The square root of 991615 is about 995.7986744317. The cubic root of 991615 is about 99.7197151379.

The spelling of 991615 in words is "nine hundred ninety-one thousand, six hundred fifteen".