991131 has 8 divisors (see below), whose sum is σ = 1341504. Its totient is φ = 650760.

The previous prime is 991129. The next prime is 991147. The reversal of 991131 is 131199.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 991131 - 2¹ = 991129 is a prime.

It is a super-2 number, since 2×991131² = 1964681318322, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (991171) 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, 2265 + ... + 2666.

It is an arithmetic number, because the mean of its divisors is an integer number (167688).

2⁹⁹¹¹³¹ is an apocalyptic number.

991131 is a deficient number, since it is larger than the sum of its proper divisors (350373).

991131 is a wasteful number, since it uses less digits than its factorization.

991131 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5001.

The product of its digits is 243, while the sum is 24.

The square root of 991131 is about 995.5556237599. Note that the first 3 decimals coincide. The cubic root of 991131 is about 99.7034883440.

The spelling of 991131 in words is "nine hundred ninety-one thousand, one hundred thirty-one".