81666071 has 2 divisors, whose sum is σ = 81666072. Its totient is φ = 81666070.

The previous prime is 81666041. The next prime is 81666131. The reversal of 81666071 is 17066618.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 81666071 - 2¹⁰ = 81665047 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81666041) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40833035 + 40833036.

It is an arithmetic number, because the mean of its divisors is an integer number (40833036).

Almost surely, 2^81666071 is an apocalyptic number.

81666071 is a deficient number, since it is larger than the sum of its proper divisors (1).

81666071 is an equidigital number, since it uses as much as digits as its factorization.

81666071 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 12096, while the sum is 35.

The square root of 81666071 is about 9036.9281838465. The cubic root of 81666071 is about 433.8576111289.

The spelling of 81666071 in words is "eighty-one million, six hundred sixty-six thousand, seventy-one".