81461665 has 8 divisors (see below), whose sum is σ = 97870248. Its totient is φ = 65091840.

The previous prime is 81461663. The next prime is 81461687. The reversal of 81461665 is 56616418.

It can be written as a sum of positive squares in 4 ways, for example, as 767376 + 80694289 = 876^2 + 8983^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 81461665 - 2¹ = 81461663 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81461663) by changing a digit.

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 7 ways as a sum of consecutive naturals, for example, 4842 + ... + 13651.

It is an arithmetic number, because the mean of its divisors is an integer number (12233781).

Almost surely, 2^81461665 is an apocalyptic number.

It is an amenable number.

81461665 is a deficient number, since it is larger than the sum of its proper divisors (16408583).

81461665 is a wasteful number, since it uses less digits than its factorization.

81461665 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 19379.

The product of its digits is 34560, while the sum is 37.

The square root of 81461665 is about 9025.6116136249. The cubic root of 81461665 is about 433.4953342348.

The spelling of 81461665 in words is "eighty-one million, four hundred sixty-one thousand, six hundred sixty-five".