816910921 has 2 divisors, whose sum is σ = 816910922. Its totient is φ = 816910920.

The previous prime is 816910883. The next prime is 816910933. The reversal of 816910921 is 129019618.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 449652025 + 367258896 = 21205^2 + 19164^2 .

It is a cyclic number.

It is not a de Polignac number, because 816910921 - 2¹⁷ = 816779849 is a prime.

It is not a weakly prime, because it can be changed into another prime (816910951) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 408455460 + 408455461.

It is an arithmetic number, because the mean of its divisors is an integer number (408455461).

Almost surely, 2^816910921 is an apocalyptic number.

It is an amenable number.

816910921 is a deficient number, since it is larger than the sum of its proper divisors (1).

816910921 is an equidigital number, since it uses as much as digits as its factorization.

816910921 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 7776, while the sum is 37.

The square root of 816910921 is about 28581.6535735776. The cubic root of 816910921 is about 934.8133387757.

The spelling of 816910921 in words is "eight hundred sixteen million, nine hundred ten thousand, nine hundred twenty-one".