208921 has 4 divisors (see below), whose sum is σ = 209844. Its totient is φ = 208000.

The previous prime is 208907. The next prime is 208927. The reversal of 208921 is 129802.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 129802 = 2 ⋅64901.

It can be written as a sum of positive squares in 2 ways, for example, as 151321 + 57600 = 389^2 + 240^2 .

It is a cyclic number.

It is not a de Polignac number, because 208921 - 2⁵ = 208889 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 208892 and 208901.

It is not an unprimeable number, because it can be changed into a prime (208927) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 141 + ... + 661.

It is an arithmetic number, because the mean of its divisors is an integer number (52461).

2²⁰⁸⁹²¹ is an apocalyptic number.

It is an amenable number.

208921 is a deficient number, since it is larger than the sum of its proper divisors (923).

208921 is an equidigital number, since it uses as much as digits as its factorization.

208921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 922.

The product of its (nonzero) digits is 288, while the sum is 22.

The square root of 208921 is about 457.0787678289. The cubic root of 208921 is about 59.3372432161.

The spelling of 208921 in words is "two hundred eight thousand, nine hundred twenty-one".