208666621 has 2 divisors, whose sum is σ = 208666622. Its totient is φ = 208666620.

The previous prime is 208666613. The next prime is 208666637. The reversal of 208666621 is 126666802.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 140422500 + 68244121 = 11850^2 + 8261^2 .

It is a cyclic number.

It is not a de Polignac number, because 208666621 - 2³ = 208666613 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (208666651) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 104333310 + 104333311.

It is an arithmetic number, because the mean of its divisors is an integer number (104333311).

Almost surely, 2^208666621 is an apocalyptic number.

It is an amenable number.

208666621 is a deficient number, since it is larger than the sum of its proper divisors (1).

208666621 is an equidigital number, since it uses as much as digits as its factorization.

208666621 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 41472, while the sum is 37.

The square root of 208666621 is about 14445.2975393378. The cubic root of 208666621 is about 593.1315072998.

The spelling of 208666621 in words is "two hundred eight million, six hundred sixty-six thousand, six hundred twenty-one".