2005801781 has 2 divisors, whose sum is σ = 2005801782. Its totient is φ = 2005801780.

The previous prime is 2005801771. The next prime is 2005801807. The reversal of 2005801781 is 1871085002.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1410002500 + 595799281 = 37550^2 + 24409^2 .

It is a cyclic number.

It is not a de Polignac number, because 2005801781 - 2⁶ = 2005801717 is a prime.

It is a super-2 number, since 2×2005801781² = 8046481569325543922, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (2005801771) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1002900890 + 1002900891.

It is an arithmetic number, because the mean of its divisors is an integer number (1002900891).

Almost surely, 2^2005801781 is an apocalyptic number.

It is an amenable number.

2005801781 is a deficient number, since it is larger than the sum of its proper divisors (1).

2005801781 is an equidigital number, since it uses as much as digits as its factorization.

2005801781 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 4480, while the sum is 32.

The square root of 2005801781 is about 44786.1784594310. The cubic root of 2005801781 is about 1261.1381714085.

Adding to 2005801781 its reverse (1871085002), we get a palindrome (3876886783).

The spelling of 2005801781 in words is "two billion, five million, eight hundred one thousand, seven hundred eighty-one".