81647985 has 16 divisors (see below), whose sum is σ = 130916736. Its totient is φ = 43452288.

The previous prime is 81647971. The next prime is 81648031. The reversal of 81647985 is 58974618.

It is not a de Polignac number, because 81647985 - 2⁷ = 81647857 is a prime.

It is a Curzon number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1717 + ... + 12893.

It is an arithmetic number, because the mean of its divisors is an integer number (8182296).

Almost surely, 2^81647985 is an apocalyptic number.

It is an amenable number.

81647985 is a deficient number, since it is larger than the sum of its proper divisors (49268751).

81647985 is a wasteful number, since it uses less digits than its factorization.

81647985 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11672.

The product of its digits is 483840, while the sum is 48.

The square root of 81647985 is about 9035.9274565481. The cubic root of 81647985 is about 433.8255809847.

The spelling of 81647985 in words is "eighty-one million, six hundred forty-seven thousand, nine hundred eighty-five".