209801861 has 2 divisors, whose sum is σ = 209801862. Its totient is φ = 209801860.

The previous prime is 209801759. The next prime is 209801869. The reversal of 209801861 is 168108902.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 195132961 + 14668900 = 13969^2 + 3830^2 .

It is a cyclic number.

It is not a de Polignac number, because 209801861 - 2¹⁰ = 209800837 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (209801869) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 104900930 + 104900931.

It is an arithmetic number, because the mean of its divisors is an integer number (104900931).

Almost surely, 2^209801861 is an apocalyptic number.

It is an amenable number.

209801861 is a deficient number, since it is larger than the sum of its proper divisors (1).

209801861 is an equidigital number, since it uses as much as digits as its factorization.

209801861 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 6912, while the sum is 35.

The square root of 209801861 is about 14484.5386878561. The cubic root of 209801861 is about 594.2051963323.

The spelling of 209801861 in words is "two hundred nine million, eight hundred one thousand, eight hundred sixty-one".