81585505 has 8 divisors (see below), whose sum is σ = 98086824. Its totient is φ = 65145600.

The previous prime is 81585503. The next prime is 81585509. The reversal of 81585505 is 50558518.

It can be written as a sum of positive squares in 4 ways, for example, as 14197824 + 67387681 = 3768^2 + 8209^2 .

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

It is not a de Polignac number, because 81585505 - 2¹ = 81585503 is a prime.

It is a super-2 number, since 2×81585505² = 13312389252210050, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81585503) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 12376 + ... + 17785.

It is an arithmetic number, because the mean of its divisors is an integer number (12260853).

Almost surely, 2^81585505 is an apocalyptic number.

It is an amenable number.

81585505 is a deficient number, since it is larger than the sum of its proper divisors (16501319).

81585505 is a wasteful number, since it uses less digits than its factorization.

81585505 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 30707.

The product of its (nonzero) digits is 40000, while the sum is 37.

The square root of 81585505 is about 9032.4694851408. The cubic root of 81585505 is about 433.7148930551.

It can be divided in two parts, 815 and 85505, that added together give a triangular number (86320 = T₄₁₅).

The spelling of 81585505 in words is "eighty-one million, five hundred eighty-five thousand, five hundred five".