6517991 has 4 divisors (see below), whose sum is σ = 6554184. Its totient is φ = 6481800.

The previous prime is 6517981. The next prime is 6517997. The reversal of 6517991 is 1997156.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-6517991 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (6517997) 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, 17825 + ... + 18186.

It is an arithmetic number, because the mean of its divisors is an integer number (1638546).

Almost surely, 2^6517991 is an apocalyptic number.

6517991 is a deficient number, since it is larger than the sum of its proper divisors (36193).

6517991 is a wasteful number, since it uses less digits than its factorization.

6517991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 36192.

The product of its digits is 17010, while the sum is 38.

The square root of 6517991 is about 2553.0356440912. The cubic root of 6517991 is about 186.7975828363.

The spelling of 6517991 in words is "six million, five hundred seventeen thousand, nine hundred ninety-one".