81971873 has 2 divisors, whose sum is σ = 81971874. Its totient is φ = 81971872.

The previous prime is 81971863. The next prime is 81971917. The reversal of 81971873 is 37817918.

It is an a-pointer prime, because the next prime (81971917) can be obtained adding 81971873 to its sum of digits (44).

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 76877824 + 5094049 = 8768^2 + 2257^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81971873 is a prime.

It is not a weakly prime, because it can be changed into another prime (81971863) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40985936 + 40985937.

It is an arithmetic number, because the mean of its divisors is an integer number (40985937).

Almost surely, 2^81971873 is an apocalyptic number.

It is an amenable number.

81971873 is a deficient number, since it is larger than the sum of its proper divisors (1).

81971873 is an equidigital number, since it uses as much as digits as its factorization.

81971873 is an evil number, because the sum of its binary digits is even.

The product of its digits is 84672, while the sum is 44.

The square root of 81971873 is about 9053.8319511685. The cubic root of 81971873 is about 434.3984692252.

The spelling of 81971873 in words is "eighty-one million, nine hundred seventy-one thousand, eight hundred seventy-three".