2005785781 has 2 divisors, whose sum is σ = 2005785782. Its totient is φ = 2005785780.

The previous prime is 2005785757. The next prime is 2005785797. The reversal of 2005785781 is 1875875002.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1663905681 + 341880100 = 40791^2 + 18490^2 .

It is a cyclic number.

It is not a de Polignac number, because 2005785781 - 2⁹ = 2005785269 is a prime.

It is a super-2 number, since 2×2005785781² = 8046353198523559922, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (2005786781) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1002892890 + 1002892891.

It is an arithmetic number, because the mean of its divisors is an integer number (1002892891).

Almost surely, 2^2005785781 is an apocalyptic number.

It is an amenable number.

2005785781 is a deficient number, since it is larger than the sum of its proper divisors (1).

2005785781 is an equidigital number, since it uses as much as digits as its factorization.

2005785781 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 156800, while the sum is 43.

The square root of 2005785781 is about 44785.9998325370. Note that the first 3 decimals coincide. The cubic root of 2005785781 is about 1261.1348180921.

The spelling of 2005785781 in words is "two billion, five million, seven hundred eighty-five thousand, seven hundred eighty-one".