81109001 has 2 divisors, whose sum is σ = 81109002. Its totient is φ = 81109000.

The previous prime is 81108991. The next prime is 81109003. The reversal of 81109001 is 10090118.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 78783376 + 2325625 = 8876^2 + 1525^2 .

It is a cyclic number.

It is not a de Polignac number, because 81109001 - 2¹⁰ = 81107977 is a prime.

Together with 81109003, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (81109003) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40554500 + 40554501.

It is an arithmetic number, because the mean of its divisors is an integer number (40554501).

Almost surely, 2^81109001 is an apocalyptic number.

It is an amenable number.

81109001 is a deficient number, since it is larger than the sum of its proper divisors (1).

81109001 is an equidigital number, since it uses as much as digits as its factorization.

81109001 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 72, while the sum is 20.

The square root of 81109001 is about 9006.0535752348. The cubic root of 81109001 is about 432.8688663773.

Adding to 81109001 its reverse (10090118), we get a palindrome (91199119).

The spelling of 81109001 in words is "eighty-one million, one hundred nine thousand, one".