991709 has 4 divisors (see below), whose sum is σ = 1014816. Its totient is φ = 968604.

The previous prime is 991703. The next prime is 991717. The reversal of 991709 is 907199.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 991709 - 2⁴ = 991693 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 991709.

It is not an unprimeable number, because it can be changed into a prime (991703) 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, 11489 + ... + 11574.

It is an arithmetic number, because the mean of its divisors is an integer number (253704).

2⁹⁹¹⁷⁰⁹ is an apocalyptic number.

It is an amenable number.

991709 is a deficient number, since it is larger than the sum of its proper divisors (23107).

991709 is a wasteful number, since it uses less digits than its factorization.

991709 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 23106.

The product of its (nonzero) digits is 5103, while the sum is 35.

The square root of 991709 is about 995.8458716087. The cubic root of 991709 is about 99.7228660103.

The spelling of 991709 in words is "nine hundred ninety-one thousand, seven hundred nine".