991385 has 4 divisors (see below), whose sum is σ = 1189668. Its totient is φ = 793104.

The previous prime is 991381. The next prime is 991387. The reversal of 991385 is 583199.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 583199 = 233 ⋅2503.

It can be written as a sum of positive squares in 2 ways, for example, as 183184 + 808201 = 428^2 + 899^2 .

It is a cyclic number.

It is not a de Polignac number, because 991385 - 2² = 991381 is a prime.

It is a Duffinian number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 991385.

It is not an unprimeable number, because it can be changed into a prime (991381) 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, 99134 + ... + 99143.

It is an arithmetic number, because the mean of its divisors is an integer number (297417).

2⁹⁹¹³⁸⁵ is an apocalyptic number.

It is an amenable number.

991385 is a deficient number, since it is larger than the sum of its proper divisors (198283).

991385 is a wasteful number, since it uses less digits than its factorization.

991385 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 198282.

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

The square root of 991385 is about 995.6831825435. The cubic root of 991385 is about 99.7120047167.

The spelling of 991385 in words is "nine hundred ninety-one thousand, three hundred eighty-five".