81323645 has 24 divisors (see below), whose sum is σ = 106519176. Its totient is φ = 59574528.

The previous prime is 81323609. The next prime is 81323647. The reversal of 81323645 is 54632318.

It can be written as a sum of positive squares in 12 ways, for example, as 76510009 + 4813636 = 8747^2 + 2194^2 .

It is not a de Polignac number, because 81323645 - 2⁶ = 81323581 is a prime.

It is a super-2 number, since 2×81323645² = 13227070472172050, which contains 22 as substring.

It is a hoax number, since the sum of its digits (32) coincides with the sum of the digits of its distinct prime factors.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81323647) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 132359 + ... + 132971.

It is an arithmetic number, because the mean of its divisors is an integer number (4438299).

Almost surely, 2^81323645 is an apocalyptic number.

It is an amenable number.

81323645 is a deficient number, since it is larger than the sum of its proper divisors (25195531).

81323645 is a wasteful number, since it uses less digits than its factorization.

81323645 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 801 (or 788 counting only the distinct ones).

The product of its digits is 17280, while the sum is 32.

The square root of 81323645 is about 9017.9623529931. The cubic root of 81323645 is about 433.2503730074.

The spelling of 81323645 in words is "eighty-one million, three hundred twenty-three thousand, six hundred forty-five".