168020821 has 2 divisors, whose sum is σ = 168020822. Its totient is φ = 168020820.

The previous prime is 168020807. The next prime is 168020903. The reversal of 168020821 is 128020861.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 86750596 + 81270225 = 9314^2 + 9015^2 .

It is an emirp because it is prime and its reverse (128020861) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 168020821 - 2⁵ = 168020789 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 168020821.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (168020521) 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, 84010410 + 84010411.

It is an arithmetic number, because the mean of its divisors is an integer number (84010411).

Almost surely, 2^168020821 is an apocalyptic number.

It is an amenable number.

168020821 is a deficient number, since it is larger than the sum of its proper divisors (1).

168020821 is an equidigital number, since it uses as much as digits as its factorization.

168020821 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1536, while the sum is 28.

The square root of 168020821 is about 12962.2845594440. The cubic root of 168020821 is about 551.8076293982.

The spelling of 168020821 in words is "one hundred sixty-eight million, twenty thousand, eight hundred twenty-one".