81666671 has 2 divisors, whose sum is σ = 81666672. Its totient is φ = 81666670.

The previous prime is 81666661. The next prime is 81666701. The reversal of 81666671 is 17666618.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 81666671 - 2¹⁸ = 81404527 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81666601) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40833335 + 40833336.

It is an arithmetic number, because the mean of its divisors is an integer number (40833336).

Almost surely, 2^81666671 is an apocalyptic number.

81666671 is a deficient number, since it is larger than the sum of its proper divisors (1).

81666671 is an equidigital number, since it uses as much as digits as its factorization.

81666671 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 72576, while the sum is 41.

The square root of 81666671 is about 9036.9613809067. The cubic root of 81666671 is about 433.8586736425.

The spelling of 81666671 in words is "eighty-one million, six hundred sixty-six thousand, six hundred seventy-one".