216879809 has 2 divisors, whose sum is σ = 216879810. Its totient is φ = 216879808.

The previous prime is 216879797. The next prime is 216879823. The reversal of 216879809 is 908978612.

216879809 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 143400625 + 73479184 = 11975^2 + 8572^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-216879809 is a prime.

It is not a weakly prime, because it can be changed into another prime (216879899) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 108439904 + 108439905.

It is an arithmetic number, because the mean of its divisors is an integer number (108439905).

Almost surely, 2^216879809 is an apocalyptic number.

It is an amenable number.

216879809 is a deficient number, since it is larger than the sum of its proper divisors (1).

216879809 is an equidigital number, since it uses as much as digits as its factorization.

216879809 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 435456, while the sum is 50.

The square root of 216879809 is about 14726.8397492470. The cubic root of 216879809 is about 600.8135344007.

The spelling of 216879809 in words is "two hundred sixteen million, eight hundred seventy-nine thousand, eight hundred nine".