81287189 has 2 divisors, whose sum is σ = 81287190. Its totient is φ = 81287188.

The previous prime is 81287069. The next prime is 81287201. The reversal of 81287189 is 98178218.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 80694289 + 592900 = 8983^2 + 770^2 .

It is a cyclic number.

It is not a de Polignac number, because 81287189 - 2¹² = 81283093 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81280189) 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, 40643594 + 40643595.

It is an arithmetic number, because the mean of its divisors is an integer number (40643595).

Almost surely, 2^81287189 is an apocalyptic number.

It is an amenable number.

81287189 is a deficient number, since it is larger than the sum of its proper divisors (1).

81287189 is an equidigital number, since it uses as much as digits as its factorization.

81287189 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 64512, while the sum is 44.

The square root of 81287189 is about 9015.9408272237. The cubic root of 81287189 is about 433.1856237522.

The spelling of 81287189 in words is "eighty-one million, two hundred eighty-seven thousand, one hundred eighty-nine".