8216921 has 2 divisors, whose sum is σ = 8216922. Its totient is φ = 8216920.

The previous prime is 8216893. The next prime is 8216927. The reversal of 8216921 is 1296128.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 8065600 + 151321 = 2840^2 + 389^2 .

It is a cyclic number.

It is not a de Polignac number, because 8216921 - 2¹⁰ = 8215897 is a prime.

It is an Ulam number.

It is not a weakly prime, because it can be changed into another prime (8216927) 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, 4108460 + 4108461.

It is an arithmetic number, because the mean of its divisors is an integer number (4108461).

Almost surely, 2^8216921 is an apocalyptic number.

It is an amenable number.

8216921 is a deficient number, since it is larger than the sum of its proper divisors (1).

8216921 is an equidigital number, since it uses as much as digits as its factorization.

8216921 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1728, while the sum is 29.

The square root of 8216921 is about 2866.5172247869. The cubic root of 8216921 is about 201.7915783147.

The spelling of 8216921 in words is "eight million, two hundred sixteen thousand, nine hundred twenty-one".