81671745 has 16 divisors (see below), whose sum is σ = 130821120. Its totient is φ = 43509504.

The previous prime is 81671729. The next prime is 81671771. The reversal of 81671745 is 54717618.

It is not a de Polignac number, because 81671745 - 2⁴ = 81671729 is a prime.

It is a Curzon number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 13801 + ... + 18809.

It is an arithmetic number, because the mean of its divisors is an integer number (8176320).

Almost surely, 2^81671745 is an apocalyptic number.

It is an amenable number.

81671745 is a deficient number, since it is larger than the sum of its proper divisors (49149375).

81671745 is a wasteful number, since it uses less digits than its factorization.

81671745 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6104.

The product of its digits is 47040, while the sum is 39.

The square root of 81671745 is about 9037.2421125031. The cubic root of 81671745 is about 433.8676587576.

The spelling of 81671745 in words is "eighty-one million, six hundred seventy-one thousand, seven hundred forty-five".