204778391 has 2 divisors, whose sum is σ = 204778392. Its totient is φ = 204778390.

The previous prime is 204778381. The next prime is 204778393. The reversal of 204778391 is 193877402.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 204778391 - 2¹⁰ = 204777367 is a prime.

It is a Sophie Germain prime.

Together with 204778393, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (204778393) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 102389195 + 102389196.

It is an arithmetic number, because the mean of its divisors is an integer number (102389196).

Almost surely, 2^204778391 is an apocalyptic number.

204778391 is a deficient number, since it is larger than the sum of its proper divisors (1).

204778391 is an equidigital number, since it uses as much as digits as its factorization.

204778391 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 84672, while the sum is 41.

The square root of 204778391 is about 14310.0800486929. The cubic root of 204778391 is about 589.4243077417.

The spelling of 204778391 in words is "two hundred four million, seven hundred seventy-eight thousand, three hundred ninety-one".