243351991 has 16 divisors (see below), whose sum is σ = 264298464. Its totient is φ = 223202304.

The previous prime is 243351971. The next prime is 243352009. The reversal of 243351991 is 199153342.

It is a cyclic number.

It is not a de Polignac number, because 243351991 - 2⁵ = 243351959 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 243351991.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (243351971) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 146035 + ... + 147691.

It is an arithmetic number, because the mean of its divisors is an integer number (16518654).

Almost surely, 2^243351991 is an apocalyptic number.

243351991 is a deficient number, since it is larger than the sum of its proper divisors (20946473).

243351991 is a wasteful number, since it uses less digits than its factorization.

243351991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1890.

The product of its digits is 29160, while the sum is 37.

The square root of 243351991 is about 15599.7432991700. The cubic root of 243351991 is about 624.3263064000.

The spelling of 243351991 in words is "two hundred forty-three million, three hundred fifty-one thousand, nine hundred ninety-one".