81971585 has 8 divisors (see below), whose sum is σ = 99611520. Its totient is φ = 64746864.

The previous prime is 81971579. The next prime is 81971629. The reversal of 81971585 is 58517918.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 81971585 - 2⁶ = 81971521 is a prime.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 103367 + ... + 104156.

It is an arithmetic number, because the mean of its divisors is an integer number (12451440).

Almost surely, 2^81971585 is an apocalyptic number.

It is an amenable number.

81971585 is a deficient number, since it is larger than the sum of its proper divisors (17639935).

81971585 is a wasteful number, since it uses less digits than its factorization.

81971585 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 207607.

The product of its digits is 100800, while the sum is 44.

The square root of 81971585 is about 9053.8160462868. The cubic root of 81971585 is about 434.3979604860.

The spelling of 81971585 in words is "eighty-one million, nine hundred seventy-one thousand, five hundred eighty-five".