81508609 has 24 divisors (see below), whose sum is σ = 102782400. Its totient is φ = 64066464.

The previous prime is 81508597. The next prime is 81508621. The reversal of 81508609 is 90680518.

It is an interprime number because it is at equal distance from previous prime (81508597) and next prime (81508621).

It is not a de Polignac number, because 81508609 - 2⁵ = 81508577 is a prime.

It is a super-2 number, since 2×81508609² = 13287306682229762, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81508699) by changing a digit.

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 23 ways as a sum of consecutive naturals, for example, 126442 + ... + 127084.

It is an arithmetic number, because the mean of its divisors is an integer number (4282600).

Almost surely, 2^81508609 is an apocalyptic number.

It is an amenable number.

81508609 is a deficient number, since it is larger than the sum of its proper divisors (21273791).

81508609 is a wasteful number, since it uses less digits than its factorization.

81508609 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 869 (or 862 counting only the distinct ones).

The product of its (nonzero) digits is 17280, while the sum is 37.

The square root of 81508609 is about 9028.2118384539. The cubic root of 81508609 is about 433.5785885163.

The spelling of 81508609 in words is "eighty-one million, five hundred eight thousand, six hundred nine".