209998981 has 2 divisors, whose sum is σ = 209998982. Its totient is φ = 209998980.

The previous prime is 209998969. The next prime is 209999017. The reversal of 209998981 is 189899902.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 198669025 + 11329956 = 14095^2 + 3366^2 .

It is a cyclic number.

It is not a de Polignac number, because 209998981 - 2⁷ = 209998853 is a prime.

It is a super-2 number, since 2×209998981² = 88199144042076722, which contains 22 as substring.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (209998781) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 104999490 + 104999491.

It is an arithmetic number, because the mean of its divisors is an integer number (104999491).

Almost surely, 2^209998981 is an apocalyptic number.

It is an amenable number.

209998981 is a deficient number, since it is larger than the sum of its proper divisors (1).

209998981 is an equidigital number, since it uses as much as digits as its factorization.

209998981 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 839808, while the sum is 55.

The square root of 209998981 is about 14491.3415873065. The cubic root of 209998981 is about 594.3912338690.

The spelling of 209998981 in words is "two hundred nine million, nine hundred ninety-eight thousand, nine hundred eighty-one".