991517 has 4 divisors (see below), whose sum is σ = 1001436. Its totient is φ = 981600.

The previous prime is 991511. The next prime is 991531. The reversal of 991517 is 715199.

991517 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 715199 = 47 ⋅15217.

It can be written as a sum of positive squares in 2 ways, for example, as 972196 + 19321 = 986^2 + 139^2 .

It is a cyclic number.

It is not a de Polignac number, because 991517 - 2⁶ = 991453 is a prime.

It is a super-2 number, since 2×991517² = 1966211922578, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (991511) 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, 4808 + ... + 5009.

It is an arithmetic number, because the mean of its divisors is an integer number (250359).

2⁹⁹¹⁵¹⁷ is an apocalyptic number.

It is an amenable number.

991517 is a deficient number, since it is larger than the sum of its proper divisors (9919).

991517 is a wasteful number, since it uses less digits than its factorization.

991517 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9918.

The product of its digits is 2835, while the sum is 32.

The square root of 991517 is about 995.7494664824. The cubic root of 991517 is about 99.7164299738.

The spelling of 991517 in words is "nine hundred ninety-one thousand, five hundred seventeen".