81571121 has 2 divisors, whose sum is σ = 81571122. Its totient is φ = 81571120.

The previous prime is 81571109. The next prime is 81571141. The reversal of 81571121 is 12117518.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 67881121 + 13690000 = 8239^2 + 3700^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81571121 is a prime.

It is not a weakly prime, because it can be changed into another prime (81571141) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40785560 + 40785561.

It is an arithmetic number, because the mean of its divisors is an integer number (40785561).

Almost surely, 2^81571121 is an apocalyptic number.

It is an amenable number.

81571121 is a deficient number, since it is larger than the sum of its proper divisors (1).

81571121 is an equidigital number, since it uses as much as digits as its factorization.

81571121 is an evil number, because the sum of its binary digits is even.

The product of its digits is 560, while the sum is 26.

The square root of 81571121 is about 9031.6732115373. The cubic root of 81571121 is about 433.6894027359.

Adding to 81571121 its reverse (12117518), we get a palindrome (93688639).

The spelling of 81571121 in words is "eighty-one million, five hundred seventy-one thousand, one hundred twenty-one".