81521175289 has 2 divisors, whose sum is σ = 81521175290. Its totient is φ = 81521175288.

The previous prime is 81521175187. The next prime is 81521175311. The reversal of 81521175289 is 98257112518.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 42556389264 + 38964786025 = 206292^2 + 197395^2 .

It is a cyclic number.

It is not a de Polignac number, because 81521175289 - 2¹³ = 81521167097 is a prime.

It is not a weakly prime, because it can be changed into another prime (81521175889) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40760587644 + 40760587645.

It is an arithmetic number, because the mean of its divisors is an integer number (40760587645).

Almost surely, 2^81521175289 is an apocalyptic number.

It is an amenable number.

81521175289 is a deficient number, since it is larger than the sum of its proper divisors (1).

81521175289 is an equidigital number, since it uses as much as digits as its factorization.

81521175289 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 403200, while the sum is 49.

The spelling of 81521175289 in words is "eighty-one billion, five hundred twenty-one million, one hundred seventy-five thousand, two hundred eighty-nine".