817729921 has 2 divisors, whose sum is σ = 817729922. Its totient is φ = 817729920.

The previous prime is 817729901. The next prime is 817729963. The reversal of 817729921 is 129927718.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 809687025 + 8042896 = 28455^2 + 2836^2 .

It is a cyclic number.

It is not a de Polignac number, because 817729921 - 2²⁹ = 280859009 is a prime.

It is not a weakly prime, because it can be changed into another prime (817729901) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 408864960 + 408864961.

It is an arithmetic number, because the mean of its divisors is an integer number (408864961).

Almost surely, 2^817729921 is an apocalyptic number.

It is an amenable number.

817729921 is a deficient number, since it is larger than the sum of its proper divisors (1).

817729921 is an equidigital number, since it uses as much as digits as its factorization.

817729921 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 127008, while the sum is 46.

The square root of 817729921 is about 28595.9773569640. The cubic root of 817729921 is about 935.1256357433.

The spelling of 817729921 in words is "eight hundred seventeen million, seven hundred twenty-nine thousand, nine hundred twenty-one".