209836681 has 2 divisors, whose sum is σ = 209836682. Its totient is φ = 209836680.

The previous prime is 209836637. The next prime is 209836687. The reversal of 209836681 is 186638902.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 190992400 + 18844281 = 13820^2 + 4341^2 .

It is a cyclic number.

It is not a de Polignac number, because 209836681 - 2⁷ = 209836553 is a prime.

It is a super-2 number, since 2×209836681² = 88062865386191522, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (209836687) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 104918340 + 104918341.

It is an arithmetic number, because the mean of its divisors is an integer number (104918341).

Almost surely, 2^209836681 is an apocalyptic number.

It is an amenable number.

209836681 is a deficient number, since it is larger than the sum of its proper divisors (1).

209836681 is an equidigital number, since it uses as much as digits as its factorization.

209836681 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 124416, while the sum is 43.

The square root of 209836681 is about 14485.7406093027. The cubic root of 209836681 is about 594.2380671567.

The spelling of 209836681 in words is "two hundred nine million, eight hundred thirty-six thousand, six hundred eighty-one".