209106661 has 2 divisors, whose sum is σ = 209106662. Its totient is φ = 209106660.

The previous prime is 209106659. The next prime is 209106671. The reversal of 209106661 is 166601902.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 204776100 + 4330561 = 14310^2 + 2081^2 .

It is a cyclic number.

It is not a de Polignac number, because 209106661 - 2¹ = 209106659 is a prime.

Together with 209106659, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (209106671) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 104553330 + 104553331.

It is an arithmetic number, because the mean of its divisors is an integer number (104553331).

Almost surely, 2^209106661 is an apocalyptic number.

It is an amenable number.

209106661 is a deficient number, since it is larger than the sum of its proper divisors (1).

209106661 is an equidigital number, since it uses as much as digits as its factorization.

209106661 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 3888, while the sum is 31.

The square root of 209106661 is about 14460.5207720884. The cubic root of 209106661 is about 593.5481500983.

The spelling of 209106661 in words is "two hundred nine million, one hundred six thousand, six hundred sixty-one".