991143 has 8 divisors (see below), whose sum is σ = 1468400. Its totient is φ = 660744.

The previous prime is 991129. The next prime is 991147. The reversal of 991143 is 341199.

It is not a de Polignac number, because 991143 - 2⁴ = 991127 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27), and also a Moran number because the ratio is a prime number: 36709 = 991143 / (9 + 9 + 1 + 1 + 4 + 3).

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (991147) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 18328 + ... + 18381.

It is an arithmetic number, because the mean of its divisors is an integer number (183550).

2⁹⁹¹¹⁴³ is an apocalyptic number.

991143 is a deficient number, since it is larger than the sum of its proper divisors (477257).

991143 is a wasteful number, since it uses less digits than its factorization.

991143 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 36718 (or 36712 counting only the distinct ones).

The product of its digits is 972, while the sum is 27.

The square root of 991143 is about 995.5616505270. The cubic root of 991143 is about 99.7038907251.

The spelling of 991143 in words is "nine hundred ninety-one thousand, one hundred forty-three".