216798781 has 2 divisors, whose sum is σ = 216798782. Its totient is φ = 216798780.

The previous prime is 216798761. The next prime is 216798817. The reversal of 216798781 is 187897612.

Together with next prime (216798817) it forms an Ormiston pair, because they use the same digits, order apart.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 111408025 + 105390756 = 10555^2 + 10266^2 .

It is a cyclic number.

It is not a de Polignac number, because 216798781 - 2⁷ = 216798653 is a prime.

It is a super-2 number, since 2×216798781² = 94003422886171922, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (216798731) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 108399390 + 108399391.

It is an arithmetic number, because the mean of its divisors is an integer number (108399391).

Almost surely, 2^216798781 is an apocalyptic number.

It is an amenable number.

216798781 is a deficient number, since it is larger than the sum of its proper divisors (1).

216798781 is an equidigital number, since it uses as much as digits as its factorization.

216798781 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 338688, while the sum is 49.

The square root of 216798781 is about 14724.0884607503. The cubic root of 216798781 is about 600.7387021956.

The spelling of 216798781 in words is "two hundred sixteen million, seven hundred ninety-eight thousand, seven hundred eighty-one".