81666131 has 2 divisors, whose sum is σ = 81666132. Its totient is φ = 81666130.

The previous prime is 81666071. The next prime is 81666149. The reversal of 81666131 is 13166618.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 81666131 - 2¹⁰ = 81665107 is a prime.

It is a super-2 number, since 2×81666131² = 13338713905018322, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (81666191) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40833065 + 40833066.

It is an arithmetic number, because the mean of its divisors is an integer number (40833066).

Almost surely, 2^81666131 is an apocalyptic number.

81666131 is a deficient number, since it is larger than the sum of its proper divisors (1).

81666131 is an equidigital number, since it uses as much as digits as its factorization.

81666131 is an evil number, because the sum of its binary digits is even.

The product of its digits is 5184, while the sum is 32.

The square root of 81666131 is about 9036.9315035581. The cubic root of 81666131 is about 433.8577173805.

The spelling of 81666131 in words is "eighty-one million, six hundred sixty-six thousand, one hundred thirty-one".