812120809 has 2 divisors, whose sum is σ = 812120810. Its totient is φ = 812120808.

The previous prime is 812120789. The next prime is 812120851. The reversal of 812120809 is 908021218.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 589275625 + 222845184 = 24275^2 + 14928^2 .

It is a cyclic number.

It is not a de Polignac number, because 812120809 - 2⁷ = 812120681 is a prime.

It is not a weakly prime, because it can be changed into another prime (812120879) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 406060404 + 406060405.

It is an arithmetic number, because the mean of its divisors is an integer number (406060405).

Almost surely, 2^812120809 is an apocalyptic number.

It is an amenable number.

812120809 is a deficient number, since it is larger than the sum of its proper divisors (1).

812120809 is an equidigital number, since it uses as much as digits as its factorization.

812120809 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2304, while the sum is 31.

The square root of 812120809 is about 28497.7334010970. The cubic root of 812120809 is about 932.9826040892.

The spelling of 812120809 in words is "eight hundred twelve million, one hundred twenty thousand, eight hundred nine".