216563381 has 2 divisors, whose sum is σ = 216563382. Its totient is φ = 216563380.

The previous prime is 216563339. The next prime is 216563383. The reversal of 216563381 is 183365612.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 196840900 + 19722481 = 14030^2 + 4441^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-216563381 is a prime.

It is a super-2 number, since 2×216563381² = 93799395980302322, which contains 22 as substring.

It is a Sophie Germain prime.

Together with 216563383, it forms a pair of twin primes.

It is a Chen prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (216563383) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 108281690 + 108281691.

It is an arithmetic number, because the mean of its divisors is an integer number (108281691).

Almost surely, 2^216563381 is an apocalyptic number.

It is an amenable number.

216563381 is a deficient number, since it is larger than the sum of its proper divisors (1).

216563381 is an equidigital number, since it uses as much as digits as its factorization.

216563381 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 25920, while the sum is 35.

The square root of 216563381 is about 14716.0925860094. The cubic root of 216563381 is about 600.5211962005.

The spelling of 216563381 in words is "two hundred sixteen million, five hundred sixty-three thousand, three hundred eighty-one".