216770821 has 2 divisors, whose sum is σ = 216770822. Its totient is φ = 216770820.

The previous prime is 216770797. The next prime is 216770831. The reversal of 216770821 is 128077612.

It is a happy number.

216770821 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 127373796 + 89397025 = 11286^2 + 9455^2 .

It is a cyclic number.

It is not a de Polignac number, because 216770821 - 2⁵ = 216770789 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (216770831) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 108385410 + 108385411.

It is an arithmetic number, because the mean of its divisors is an integer number (108385411).

Almost surely, 2^216770821 is an apocalyptic number.

It is an amenable number.

216770821 is a deficient number, since it is larger than the sum of its proper divisors (1).

216770821 is an equidigital number, since it uses as much as digits as its factorization.

216770821 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 9408, while the sum is 34.

The square root of 216770821 is about 14723.1389655875. The cubic root of 216770821 is about 600.7128758261.

The spelling of 216770821 in words is "two hundred sixteen million, seven hundred seventy thousand, eight hundred twenty-one".