243738991 has 2 divisors, whose sum is σ = 243738992. Its totient is φ = 243738990.

The previous prime is 243738983. The next prime is 243739003. The reversal of 243738991 is 199837342.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 243738991 - 2³ = 243738983 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (243738941) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 121869495 + 121869496.

It is an arithmetic number, because the mean of its divisors is an integer number (121869496).

Almost surely, 2^243738991 is an apocalyptic number.

243738991 is a deficient number, since it is larger than the sum of its proper divisors (1).

243738991 is an equidigital number, since it uses as much as digits as its factorization.

243738991 is an evil number, because the sum of its binary digits is even.

The product of its digits is 326592, while the sum is 46.

The square root of 243738991 is about 15612.1424218459. The cubic root of 243738991 is about 624.6570842084.

The spelling of 243738991 in words is "two hundred forty-three million, seven hundred thirty-eight thousand, nine hundred ninety-one".