81656873 has 2 divisors, whose sum is σ = 81656874. Its totient is φ = 81656872.

The previous prime is 81656819. The next prime is 81656879. The reversal of 81656873 is 37865618.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 58491904 + 23164969 = 7648^2 + 4813^2 .

It is a cyclic number.

It is not a de Polignac number, because 81656873 - 2²² = 77462569 is a prime.

It is not a weakly prime, because it can be changed into another prime (81656879) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40828436 + 40828437.

It is an arithmetic number, because the mean of its divisors is an integer number (40828437).

Almost surely, 2^81656873 is an apocalyptic number.

It is an amenable number.

81656873 is a deficient number, since it is larger than the sum of its proper divisors (1).

81656873 is an equidigital number, since it uses as much as digits as its factorization.

81656873 is an evil number, because the sum of its binary digits is even.

The product of its digits is 241920, while the sum is 44.

The square root of 81656873 is about 9036.4192576485. The cubic root of 81656873 is about 433.8413221442.

The spelling of 81656873 in words is "eighty-one million, six hundred fifty-six thousand, eight hundred seventy-three".