809767921 has 2 divisors, whose sum is σ = 809767922. Its totient is φ = 809767920.

The previous prime is 809767901. The next prime is 809767927. The reversal of 809767921 is 129767908.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 797271696 + 12496225 = 28236^2 + 3535^2 .

It is a cyclic number.

It is not a de Polignac number, because 809767921 - 2²¹ = 807670769 is a prime.

It is not a weakly prime, because it can be changed into another prime (809767927) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 404883960 + 404883961.

It is an arithmetic number, because the mean of its divisors is an integer number (404883961).

Almost surely, 2^809767921 is an apocalyptic number.

It is an amenable number.

809767921 is a deficient number, since it is larger than the sum of its proper divisors (1).

809767921 is an equidigital number, since it uses as much as digits as its factorization.

809767921 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 381024, while the sum is 49.

The square root of 809767921 is about 28456.4214369973. The cubic root of 809767921 is about 932.0807157003.

The spelling of 809767921 in words is "eight hundred nine million, seven hundred sixty-seven thousand, nine hundred twenty-one".