243995581 has 2 divisors, whose sum is σ = 243995582. Its totient is φ = 243995580.

The previous prime is 243995579. The next prime is 243995627. The reversal of 243995581 is 185599342.

It is an a-pointer prime, because the next prime (243995627) can be obtained adding 243995581 to its sum of digits (46).

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 238548025 + 5447556 = 15445^2 + 2334^2 .

It is a cyclic number.

It is not a de Polignac number, because 243995581 - 2¹ = 243995579 is a prime.

It is a super-2 number, since 2×243995581² = 119067687095055122, which contains 22 as substring.

Together with 243995579, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (243995561) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 121997790 + 121997791.

It is an arithmetic number, because the mean of its divisors is an integer number (121997791).

Almost surely, 2^243995581 is an apocalyptic number.

It is an amenable number.

243995581 is a deficient number, since it is larger than the sum of its proper divisors (1).

243995581 is an equidigital number, since it uses as much as digits as its factorization.

243995581 is an evil number, because the sum of its binary digits is even.

The product of its digits is 388800, while the sum is 46.

The square root of 243995581 is about 15620.3579024298. The cubic root of 243995581 is about 624.8762046011.

The spelling of 243995581 in words is "two hundred forty-three million, nine hundred ninety-five thousand, five hundred eighty-one".