81221471 has 2 divisors, whose sum is σ = 81221472. Its totient is φ = 81221470.

The previous prime is 81221443. The next prime is 81221507. The reversal of 81221471 is 17412218.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 81221471 - 2⁶ = 81221407 is a prime.

It is a super-3 number, since 3×81221471³ (a number of 25 digits) contains 333 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 81221471.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81221411) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40610735 + 40610736.

It is an arithmetic number, because the mean of its divisors is an integer number (40610736).

Almost surely, 2^81221471 is an apocalyptic number.

81221471 is a deficient number, since it is larger than the sum of its proper divisors (1).

81221471 is an equidigital number, since it uses as much as digits as its factorization.

81221471 is an evil number, because the sum of its binary digits is even.

The product of its digits is 896, while the sum is 26.

The square root of 81221471 is about 9012.2955455311. The cubic root of 81221471 is about 433.0688535352.

Adding to 81221471 its reverse (17412218), we get a palindrome (98633689).

The spelling of 81221471 in words is "eighty-one million, two hundred twenty-one thousand, four hundred seventy-one".