19810081 has 2 divisors, whose sum is σ = 19810082. Its totient is φ = 19810080.

The previous prime is 19810073. The next prime is 19810097. The reversal of 19810081 is 18001891.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19184400 + 625681 = 4380^2 + 791^2 .

It is an emirp because it is prime and its reverse (18001891) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 19810081 - 2³ = 19810073 is a prime.

It is a super-2 number, since 2×19810081² = 784878618453122, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (19810001) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9905040 + 9905041.

It is an arithmetic number, because the mean of its divisors is an integer number (9905041).

Almost surely, 2^19810081 is an apocalyptic number.

It is an amenable number.

19810081 is a deficient number, since it is larger than the sum of its proper divisors (1).

19810081 is an equidigital number, since it uses as much as digits as its factorization.

19810081 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 576, while the sum is 28.

The square root of 19810081 is about 4450.8517162449. The cubic root of 19810081 is about 270.5798284510.

The spelling of 19810081 in words is "nineteen million, eight hundred ten thousand, eighty-one".