917991 has 6 divisors (see below), whose sum is σ = 1326000. Its totient is φ = 611988.

The previous prime is 917971. The next prime is 917993. The reversal of 917991 is 199719.

917991 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 917991 - 2⁶ = 917927 is a prime.

It is a plaindrome in base 11.

It is a zygodrome in base 2.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (917993) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 50991 + ... + 51008.

It is an arithmetic number, because the mean of its divisors is an integer number (221000).

2⁹¹⁷⁹⁹¹ is an apocalyptic number.

917991 is a deficient number, since it is larger than the sum of its proper divisors (408009).

917991 is a wasteful number, since it uses less digits than its factorization.

917991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 102005 (or 102002 counting only the distinct ones).

The product of its digits is 5103, while the sum is 36.

The square root of 917991 is about 958.1184686666. The cubic root of 917991 is about 97.1880364283.

The spelling of 917991 in words is "nine hundred seventeen thousand, nine hundred ninety-one".