205978109 has 2 divisors, whose sum is σ = 205978110. Its totient is φ = 205978108.

The previous prime is 205978093. The next prime is 205978139. The reversal of 205978109 is 901879502.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 166978084 + 39000025 = 12922^2 + 6245^2 .

It is a cyclic number.

It is not a de Polignac number, because 205978109 - 2⁴ = 205978093 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (205978139) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 102989054 + 102989055.

It is an arithmetic number, because the mean of its divisors is an integer number (102989055).

Almost surely, 2^205978109 is an apocalyptic number.

It is an amenable number.

205978109 is a deficient number, since it is larger than the sum of its proper divisors (1).

205978109 is an equidigital number, since it uses as much as digits as its factorization.

205978109 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 45360, while the sum is 41.

The square root of 205978109 is about 14351.9374650254. The cubic root of 205978109 is about 590.5731374037.

The spelling of 205978109 in words is "two hundred five million, nine hundred seventy-eight thousand, one hundred nine".