168309821 has 8 divisors (see below), whose sum is σ = 172210104. Its totient is φ = 164436480.

The previous prime is 168309811. The next prime is 168309833. The reversal of 168309821 is 128903861.

It can be written as a sum of positive squares in 4 ways, for example, as 71995225 + 96314596 = 8485^2 + 9814^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-168309821 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (168309811) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 6185 + ... + 19361.

It is an arithmetic number, because the mean of its divisors is an integer number (21526263).

Almost surely, 2^168309821 is an apocalyptic number.

It is an amenable number.

168309821 is a deficient number, since it is larger than the sum of its proper divisors (3900283).

168309821 is a wasteful number, since it uses less digits than its factorization.

168309821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13471.

The product of its (nonzero) digits is 20736, while the sum is 38.

The square root of 168309821 is about 12973.4274962324. The cubic root of 168309821 is about 552.1238224728.

The spelling of 168309821 in words is "one hundred sixty-eight million, three hundred nine thousand, eight hundred twenty-one".