209999081 has 2 divisors, whose sum is σ = 209999082. Its totient is φ = 209999080.

The previous prime is 209999071. The next prime is 209999117. The reversal of 209999081 is 180999902.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 209989081 + 10000 = 14491^2 + 100^2 .

It is a cyclic number.

It is not a de Polignac number, because 209999081 - 2⁶ = 209999017 is a prime.

It is a super-2 number, since 2×209999081² = 88199228041689122, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (209999021) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 104999540 + 104999541.

It is an arithmetic number, because the mean of its divisors is an integer number (104999541).

Almost surely, 2^209999081 is an apocalyptic number.

It is an amenable number.

209999081 is a deficient number, since it is larger than the sum of its proper divisors (1).

209999081 is an equidigital number, since it uses as much as digits as its factorization.

209999081 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 104976, while the sum is 47.

The square root of 209999081 is about 14491.3450376423. The cubic root of 209999081 is about 594.3913282172.

The spelling of 209999081 in words is "two hundred nine million, nine hundred ninety-nine thousand, eighty-one".