991583 has 4 divisors (see below), whose sum is σ = 993648. Its totient is φ = 989520.

The previous prime is 991579. The next prime is 991603. The reversal of 991583 is 385199.

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

It is a cyclic number.

It is not a de Polignac number, because 991583 - 2² = 991579 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 991583.

It is not an unprimeable number, because it can be changed into a prime (991483) 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, 110 + ... + 1412.

It is an arithmetic number, because the mean of its divisors is an integer number (248412).

2⁹⁹¹⁵⁸³ is an apocalyptic number.

991583 is a deficient number, since it is larger than the sum of its proper divisors (2065).

991583 is a wasteful number, since it uses less digits than its factorization.

991583 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2064.

The product of its digits is 9720, while the sum is 35.

The square root of 991583 is about 995.7826067973. The cubic root of 991583 is about 99.7186424551.

The spelling of 991583 in words is "nine hundred ninety-one thousand, five hundred eighty-three".