216815857 has 2 divisors, whose sum is σ = 216815858. Its totient is φ = 216815856.

The previous prime is 216815849. The next prime is 216815867. The reversal of 216815857 is 758518612.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 134931456 + 81884401 = 11616^2 + 9049^2 .

It is a cyclic number.

It is not a de Polignac number, because 216815857 - 2³ = 216815849 is a prime.

It is not a weakly prime, because it can be changed into another prime (216815867) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 108407928 + 108407929.

It is an arithmetic number, because the mean of its divisors is an integer number (108407929).

Almost surely, 2^216815857 is an apocalyptic number.

It is an amenable number.

216815857 is a deficient number, since it is larger than the sum of its proper divisors (1).

216815857 is an equidigital number, since it uses as much as digits as its factorization.

216815857 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 134400, while the sum is 43.

The square root of 216815857 is about 14724.6683154494. The cubic root of 216815857 is about 600.7544740320.

The spelling of 216815857 in words is "two hundred sixteen million, eight hundred fifteen thousand, eight hundred fifty-seven".