209998681 has 6 divisors (see below), whose sum is σ = 216992346. Its totient is φ = 203223600.

The previous prime is 209998673. The next prime is 209998699. The reversal of 209998681 is 186899902.

It can be written as a sum of positive squares in only one way, i.e., 108493056 + 101505625 = 10416^2 + 10075^2 .

It is not a de Polignac number, because 209998681 - 2³ = 209998673 is a prime.

It is a super-2 number, since 2×209998681² = 88198892043479522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (209998781) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 108300 + ... + 110221.

It is an arithmetic number, because the mean of its divisors is an integer number (36165391).

Almost surely, 2^209998681 is an apocalyptic number.

It is an amenable number.

209998681 is a deficient number, since it is larger than the sum of its proper divisors (6993665).

209998681 is an equidigital number, since it uses as much as digits as its factorization.

209998681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 218583 (or 218552 counting only the distinct ones).

The product of its (nonzero) digits is 559872, while the sum is 52.

The square root of 209998681 is about 14491.3312362943. The cubic root of 209998681 is about 594.3909508240.

The spelling of 209998681 in words is "two hundred nine million, nine hundred ninety-eight thousand, six hundred eighty-one".