81607581 has 20 divisors (see below), whose sum is σ = 132991584. Its totient is φ = 49458600.

The previous prime is 81607579. The next prime is 81607597. The reversal of 81607581 is 18570618.

It is not a de Polignac number, because 81607581 - 2¹ = 81607579 is a prime.

It is a super-2 number, since 2×81607581² = 13319594553343122, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81607511) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 44905 + ... + 46686.

Almost surely, 2^81607581 is an apocalyptic number.

81607581 is a gapful number since it is divisible by the number (81) formed by its first and last digit.

It is an amenable number.

81607581 is a deficient number, since it is larger than the sum of its proper divisors (51384003).

81607581 is a wasteful number, since it uses less digits than its factorization.

81607581 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 91614 (or 91605 counting only the distinct ones).

The product of its (nonzero) digits is 13440, while the sum is 36.

The square root of 81607581 is about 9033.6914381663. The cubic root of 81607581 is about 433.7540087718.

The spelling of 81607581 in words is "eighty-one million, six hundred seven thousand, five hundred eighty-one".