991783 has 16 divisors (see below), whose sum is σ = 1161216. Its totient is φ = 839520.

The previous prime is 991777. The next prime is 991811. The reversal of 991783 is 387199.

991783 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a cyclic number.

It is not a de Polignac number, because 991783 - 2⁵ = 991751 is a prime.

It is a Duffinian number.

It is a plaindrome in base 15.

It is a congruent number.

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 15 ways as a sum of consecutive naturals, for example, 9216 + ... + 9322.

It is an arithmetic number, because the mean of its divisors is an integer number (72576).

2⁹⁹¹⁷⁸³ is an apocalyptic number.

991783 is a deficient number, since it is larger than the sum of its proper divisors (169433).

991783 is a wasteful number, since it uses less digits than its factorization.

991783 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 174.

The product of its digits is 13608, while the sum is 37.

The square root of 991783 is about 995.8830252595. The cubic root of 991783 is about 99.7253463443.

It can be divided in two parts, 9917 and 83, that added together give a 4-th power (10000 = 10⁴).

The spelling of 991783 in words is "nine hundred ninety-one thousand, seven hundred eighty-three".