181243781 has 2 divisors, whose sum is σ = 181243782. Its totient is φ = 181243780.

The previous prime is 181243757. The next prime is 181243787. The reversal of 181243781 is 187342181.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 178890625 + 2353156 = 13375^2 + 1534^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-181243781 is a prime.

It is a super-2 number, since 2×181243781² = 65698616302351922, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (181243787) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 90621890 + 90621891.

It is an arithmetic number, because the mean of its divisors is an integer number (90621891).

Almost surely, 2^181243781 is an apocalyptic number.

It is an amenable number.

181243781 is a deficient number, since it is larger than the sum of its proper divisors (1).

181243781 is an equidigital number, since it uses as much as digits as its factorization.

181243781 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 10752, while the sum is 35.

The square root of 181243781 is about 13462.6810479934. The cubic root of 181243781 is about 565.9191252798.

The spelling of 181243781 in words is "one hundred eighty-one million, two hundred forty-three thousand, seven hundred eighty-one".