809212861 has 2 divisors, whose sum is σ = 809212862. Its totient is φ = 809212860.

The previous prime is 809212853. The next prime is 809212867. The reversal of 809212861 is 168212908.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 546156900 + 263055961 = 23370^2 + 16219^2 .

It is a cyclic number.

It is not a de Polignac number, because 809212861 - 2³ = 809212853 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 809212861.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (809212867) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 404606430 + 404606431.

It is an arithmetic number, because the mean of its divisors is an integer number (404606431).

Almost surely, 2^809212861 is an apocalyptic number.

It is an amenable number.

809212861 is a deficient number, since it is larger than the sum of its proper divisors (1).

809212861 is an equidigital number, since it uses as much as digits as its factorization.

809212861 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 13824, while the sum is 37.

The square root of 809212861 is about 28446.6669576596. Note that the first 3 decimals coincide. The cubic root of 809212861 is about 931.8677003565.

The spelling of 809212861 in words is "eight hundred nine million, two hundred twelve thousand, eight hundred sixty-one".