81689171 has 2 divisors, whose sum is σ = 81689172. Its totient is φ = 81689170.

The previous prime is 81689129. The next prime is 81689173. The reversal of 81689171 is 17198618.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 81689171 - 2⁶ = 81689107 is a prime.

It is a Sophie Germain prime.

Together with 81689173, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (81689173) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40844585 + 40844586.

It is an arithmetic number, because the mean of its divisors is an integer number (40844586).

Almost surely, 2^81689171 is an apocalyptic number.

81689171 is a deficient number, since it is larger than the sum of its proper divisors (1).

81689171 is an equidigital number, since it uses as much as digits as its factorization.

81689171 is an evil number, because the sum of its binary digits is even.

The product of its digits is 24192, while the sum is 41.

The square root of 81689171 is about 9038.2061826449. The cubic root of 81689171 is about 433.8985141457.

The spelling of 81689171 in words is "eighty-one million, six hundred eighty-nine thousand, one hundred seventy-one".