129918209 has 2 divisors, whose sum is σ = 129918210. Its totient is φ = 129918208.

The previous prime is 129918203. The next prime is 129918277. The reversal of 129918209 is 902819921.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 112042225 + 17875984 = 10585^2 + 4228^2 .

It is an emirp because it is prime and its reverse (902819921) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 129918209 - 2⁴ = 129918193 is a prime.

It is not a weakly prime, because it can be changed into another prime (129918203) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 64959104 + 64959105.

It is an arithmetic number, because the mean of its divisors is an integer number (64959105).

Almost surely, 2^129918209 is an apocalyptic number.

It is an amenable number.

129918209 is a deficient number, since it is larger than the sum of its proper divisors (1).

129918209 is an equidigital number, since it uses as much as digits as its factorization.

129918209 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 23328, while the sum is 41.

The square root of 129918209 is about 11398.1669140261. The cubic root of 129918209 is about 506.4734394667.

The spelling of 129918209 in words is "one hundred twenty-nine million, nine hundred eighteen thousand, two hundred nine".