81321871 has 2 divisors, whose sum is σ = 81321872. Its totient is φ = 81321870.

The previous prime is 81321847. The next prime is 81321907. The reversal of 81321871 is 17812318.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 81321871 - 2⁵ = 81321839 is a prime.

It is a super-2 number, since 2×81321871² = 13226493405881282, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81321371) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40660935 + 40660936.

It is an arithmetic number, because the mean of its divisors is an integer number (40660936).

Almost surely, 2^81321871 is an apocalyptic number.

81321871 is a deficient number, since it is larger than the sum of its proper divisors (1).

81321871 is an equidigital number, since it uses as much as digits as its factorization.

81321871 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2688, while the sum is 31.

The square root of 81321871 is about 9017.8639932081. The cubic root of 81321871 is about 433.2472226659.

The spelling of 81321871 in words is "eighty-one million, three hundred twenty-one thousand, eight hundred seventy-one".