243791991 has 16 divisors (see below), whose sum is σ = 361482720. Its totient is φ = 162388800.

The previous prime is 243791987. The next prime is 243791993. The reversal of 243791991 is 199197342.

It is not a de Polignac number, because 243791991 - 2² = 243791987 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (243791993) 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, 35541 + ... + 41841.

It is an arithmetic number, because the mean of its divisors is an integer number (22592670).

Almost surely, 2^243791991 is an apocalyptic number.

243791991 is a deficient number, since it is larger than the sum of its proper divisors (117690729).

243791991 is a wasteful number, since it uses less digits than its factorization.

243791991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7743 (or 7737 counting only the distinct ones).

The product of its digits is 122472, while the sum is 45.

The square root of 243791991 is about 15613.8397263453. The cubic root of 243791991 is about 624.7023572632.

The spelling of 243791991 in words is "two hundred forty-three million, seven hundred ninety-one thousand, nine hundred ninety-one".