1981868081 has 2 divisors, whose sum is σ = 1981868082. Its totient is φ = 1981868080.

The previous prime is 1981868069. The next prime is 1981868153. The reversal of 1981868081 is 1808681891.

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., 1831069681 + 150798400 = 42791^2 + 12280^2 .

It is an emirp because it is prime and its reverse (1808681891) is a distict prime. It is also a bemirp because it and its reverse can be mirrored producing other two distinct primes, 1808981861 and 1681898081.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1981868081 is a prime.

It is a super-2 number, since 2×1981868081² = 7855602180973245122, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (1981864081) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 990934040 + 990934041.

It is an arithmetic number, because the mean of its divisors is an integer number (990934041).

Almost surely, 2^1981868081 is an apocalyptic number.

It is an amenable number.

1981868081 is a deficient number, since it is larger than the sum of its proper divisors (1).

1981868081 is an equidigital number, since it uses as much as digits as its factorization.

1981868081 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 221184, while the sum is 50.

The square root of 1981868081 is about 44518.1769730073. The cubic root of 1981868081 is about 1256.1020210802.

The spelling of 1981868081 in words is "one billion, nine hundred eighty-one million, eight hundred sixty-eight thousand, eighty-one".