243931781 has 2 divisors, whose sum is σ = 243931782. Its totient is φ = 243931780.

The previous prime is 243931717. The next prime is 243931799. The reversal of 243931781 is 187139342.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 223771681 + 20160100 = 14959^2 + 4490^2 .

It is a cyclic number.

It is not a de Polignac number, because 243931781 - 2⁶ = 243931717 is a prime.

It is a super-2 number, since 2×243931781² = 119005427563663922, which contains 22 as substring.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (243931981) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 121965890 + 121965891.

It is an arithmetic number, because the mean of its divisors is an integer number (121965891).

Almost surely, 2^243931781 is an apocalyptic number.

It is an amenable number.

243931781 is a deficient number, since it is larger than the sum of its proper divisors (1).

243931781 is an equidigital number, since it uses as much as digits as its factorization.

243931781 is an evil number, because the sum of its binary digits is even.

The product of its digits is 36288, while the sum is 38.

The square root of 243931781 is about 15618.3155621853. The cubic root of 243931781 is about 624.8217356131.

The spelling of 243931781 in words is "two hundred forty-three million, nine hundred thirty-one thousand, seven hundred eighty-one".