991143231 has 16 divisors (see below), whose sum is σ = 1506897504. Its totient is φ = 574055424.

The previous prime is 991143229. The next prime is 991143239. The reversal of 991143231 is 132341199.

It is a happy number.

It is not a de Polignac number, because 991143231 - 2¹ = 991143229 is a prime.

It is a super-2 number, since 2×991143231² = 1964729808714238722, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 991143192 and 991143201.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (991143239) 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, 746806 + ... + 748131.

It is an arithmetic number, because the mean of its divisors is an integer number (94181094).

Almost surely, 2^991143231 is an apocalyptic number.

991143231 is a deficient number, since it is larger than the sum of its proper divisors (515754273).

991143231 is a wasteful number, since it uses less digits than its factorization.

991143231 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1494970.

The product of its digits is 5832, while the sum is 33.

The square root of 991143231 is about 31482.4273365317. The cubic root of 991143231 is about 997.0389847088.

The spelling of 991143231 in words is "nine hundred ninety-one million, one hundred forty-three thousand, two hundred thirty-one".