81985645 has 16 divisors (see below), whose sum is σ = 119052288. Its totient is φ = 52911360.

The previous prime is 81985621. The next prime is 81985711. The reversal of 81985645 is 54658918.

It is not a de Polignac number, because 81985645 - 2⁷ = 81985517 is a prime.

It is a super-3 number, since 3×81985645³ (a number of 25 digits) contains 333 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 81985595 and 81985604.

It is a congruent number.

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 15 ways as a sum of consecutive naturals, for example, 68301 + ... + 69490.

It is an arithmetic number, because the mean of its divisors is an integer number (7440768).

Almost surely, 2^81985645 is an apocalyptic number.

81985645 is a gapful number since it is divisible by the number (85) formed by its first and last digit.

It is an amenable number.

81985645 is a deficient number, since it is larger than the sum of its proper divisors (37066643).

81985645 is a wasteful number, since it uses less digits than its factorization.

81985645 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 137820.

The product of its digits is 345600, while the sum is 46.

The square root of 81985645 is about 9054.5924811667. The cubic root of 81985645 is about 434.4227954584.

The spelling of 81985645 in words is "eighty-one million, nine hundred eighty-five thousand, six hundred forty-five".