81081645 has 32 divisors (see below), whose sum is σ = 138516480. Its totient is φ = 40380480.

The previous prime is 81081643. The next prime is 81081661. The reversal of 81081645 is 54618018.

It is not a de Polignac number, because 81081645 - 2¹ = 81081643 is a prime.

It is a super-3 number, since 3×81081645³ (a number of 25 digits) contains 333 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81081643) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 18232 + ... + 22238.

It is an arithmetic number, because the mean of its divisors is an integer number (4328640).

Almost surely, 2^81081645 is an apocalyptic number.

It is an amenable number.

81081645 is a deficient number, since it is larger than the sum of its proper divisors (57434835).

81081645 is a wasteful number, since it uses less digits than its factorization.

81081645 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4105.

The product of its (nonzero) digits is 7680, while the sum is 33.

The square root of 81081645 is about 9004.5346909210. The cubic root of 81081645 is about 432.8201956909.

The spelling of 81081645 in words is "eighty-one million, eighty-one thousand, six hundred forty-five".