218237561 has 2 divisors, whose sum is σ = 218237562. Its totient is φ = 218237560.

The previous prime is 218237543. The next prime is 218237563. The reversal of 218237561 is 165732812.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 206813161 + 11424400 = 14381^2 + 3380^2 .

It is a cyclic number.

It is not a de Polignac number, because 218237561 - 2²² = 214043257 is a prime.

Together with 218237563, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (218237563) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 109118780 + 109118781.

It is an arithmetic number, because the mean of its divisors is an integer number (109118781).

Almost surely, 2^218237561 is an apocalyptic number.

It is an amenable number.

218237561 is a deficient number, since it is larger than the sum of its proper divisors (1).

218237561 is an equidigital number, since it uses as much as digits as its factorization.

218237561 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 20160, while the sum is 35.

The square root of 218237561 is about 14772.8657003305. The cubic root of 218237561 is about 602.0647025962.

The spelling of 218237561 in words is "two hundred eighteen million, two hundred thirty-seven thousand, five hundred sixty-one".