991598 has 4 divisors (see below), whose sum is σ = 1487400. Its totient is φ = 495798.

The previous prime is 991579. The next prime is 991603. The reversal of 991598 is 895199.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 895199 = 73 ⋅12263.

It is a Curzon 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 991598.

It is an unprimeable number.

991598 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 247898 + ... + 247901.

It is an arithmetic number, because the mean of its divisors is an integer number (371850).

2⁹⁹¹⁵⁹⁸ is an apocalyptic number.

991598 is a deficient number, since it is larger than the sum of its proper divisors (495802).

991598 is a wasteful number, since it uses less digits than its factorization.

991598 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 495801.

The product of its digits is 29160, while the sum is 41.

The square root of 991598 is about 995.7901385332. The cubic root of 991598 is about 99.7191452780.

The spelling of 991598 in words is "nine hundred ninety-one thousand, five hundred ninety-eight".