208688561 has 2 divisors, whose sum is σ = 208688562. Its totient is φ = 208688560.

The previous prime is 208688539. The next prime is 208688563. The reversal of 208688561 is 165886802.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 175695025 + 32993536 = 13255^2 + 5744^2 .

It is a cyclic number.

It is not a de Polignac number, because 208688561 - 2¹⁰ = 208687537 is a prime.

Together with 208688563, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (208688563) 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, 104344280 + 104344281.

It is an arithmetic number, because the mean of its divisors is an integer number (104344281).

Almost surely, 2^208688561 is an apocalyptic number.

It is an amenable number.

208688561 is a deficient number, since it is larger than the sum of its proper divisors (1).

208688561 is an equidigital number, since it uses as much as digits as its factorization.

208688561 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 184320, while the sum is 44.

The square root of 208688561 is about 14446.0569360639. The cubic root of 208688561 is about 593.1522946034.

The spelling of 208688561 in words is "two hundred eight million, six hundred eighty-eight thousand, five hundred sixty-one".