81506945 has 8 divisors (see below), whose sum is σ = 105332136. Its totient is φ = 60189696.

The previous prime is 81506939. The next prime is 81506969. The reversal of 81506945 is 54960518.

It can be written as a sum of positive squares in 4 ways, for example, as 92416 + 81414529 = 304^2 + 9023^2 .

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 81506945 - 2⁶ = 81506881 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 81506899 and 81506908.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 626912 + ... + 627041.

It is an arithmetic number, because the mean of its divisors is an integer number (13166517).

Almost surely, 2^81506945 is an apocalyptic number.

It is an amenable number.

81506945 is a deficient number, since it is larger than the sum of its proper divisors (23825191).

81506945 is a wasteful number, since it uses less digits than its factorization.

81506945 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1253971.

The product of its (nonzero) digits is 43200, while the sum is 38.

The square root of 81506945 is about 9028.1196824145. The cubic root of 81506945 is about 433.5756379908.

The spelling of 81506945 in words is "eighty-one million, five hundred six thousand, nine hundred forty-five".