209213561 has 2 divisors, whose sum is σ = 209213562. Its totient is φ = 209213560.

The previous prime is 209213551. The next prime is 209213581. The reversal of 209213561 is 165312902.

209213561 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 174768400 + 34445161 = 13220^2 + 5869^2 .

It is a cyclic number.

It is not a de Polignac number, because 209213561 - 2¹⁰ = 209212537 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (209213551) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 104606780 + 104606781.

It is an arithmetic number, because the mean of its divisors is an integer number (104606781).

Almost surely, 2^209213561 is an apocalyptic number.

It is an amenable number.

209213561 is a deficient number, since it is larger than the sum of its proper divisors (1).

209213561 is an equidigital number, since it uses as much as digits as its factorization.

209213561 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 3240, while the sum is 29.

The square root of 209213561 is about 14464.2165705578. The cubic root of 209213561 is about 593.6492778954.

The spelling of 209213561 in words is "two hundred nine million, two hundred thirteen thousand, five hundred sixty-one".