81551585 has 8 divisors (see below), whose sum is σ = 99202920. Its totient is φ = 64347264.

The previous prime is 81551581. The next prime is 81551633. The reversal of 81551585 is 58515518.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 2572816 + 78978769 = 1604^2 + 8887^2 .

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 81551585 - 2² = 81551581 is a prime.

It is a super-2 number, since 2×81551585² = 13301322032024450, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (81551581) 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, 111350 + ... + 112079.

It is an arithmetic number, because the mean of its divisors is an integer number (12400365).

Almost surely, 2^81551585 is an apocalyptic number.

It is an amenable number.

81551585 is a deficient number, since it is larger than the sum of its proper divisors (17651335).

81551585 is a wasteful number, since it uses less digits than its factorization.

81551585 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 223507.

The product of its digits is 40000, while the sum is 38.

The square root of 81551585 is about 9030.5916196006. The cubic root of 81551585 is about 433.6547776033.

The spelling of 81551585 in words is "eighty-one million, five hundred fifty-one thousand, five hundred eighty-five".