16905821 has 2 divisors, whose sum is σ = 16905822. Its totient is φ = 16905820.

The previous prime is 16905787. The next prime is 16905827. The reversal of 16905821 is 12850961.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 10725625 + 6180196 = 3275^2 + 2486^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-16905821 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (16905827) 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, 8452910 + 8452911.

It is an arithmetic number, because the mean of its divisors is an integer number (8452911).

Almost surely, 2^16905821 is an apocalyptic number.

It is an amenable number.

16905821 is a deficient number, since it is larger than the sum of its proper divisors (1).

16905821 is an equidigital number, since it uses as much as digits as its factorization.

16905821 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 4320, while the sum is 32.

The square root of 16905821 is about 4111.6688825828. The cubic root of 16905821 is about 256.6524545644.

The spelling of 16905821 in words is "sixteen million, nine hundred five thousand, eight hundred twenty-one".