820417921 has 2 divisors, whose sum is σ = 820417922. Its totient is φ = 820417920.

The previous prime is 820417903. The next prime is 820417979. The reversal of 820417921 is 129714028.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 802022400 + 18395521 = 28320^2 + 4289^2 .

It is a cyclic number.

It is not a de Polignac number, because 820417921 - 2¹¹ = 820415873 is a prime.

It is not a weakly prime, because it can be changed into another prime (820417901) 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, 410208960 + 410208961.

It is an arithmetic number, because the mean of its divisors is an integer number (410208961).

Almost surely, 2^820417921 is an apocalyptic number.

It is an amenable number.

820417921 is a deficient number, since it is larger than the sum of its proper divisors (1).

820417921 is an equidigital number, since it uses as much as digits as its factorization.

820417921 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 8064, while the sum is 34.

The square root of 820417921 is about 28642.9384142060. The cubic root of 820417921 is about 936.1491474803.

The spelling of 820417921 in words is "eight hundred twenty million, four hundred seventeen thousand, nine hundred twenty-one".