81659421 has 24 divisors (see below), whose sum is σ = 123483360. Its totient is φ = 53922672.

The previous prime is 81659411. The next prime is 81659429. The reversal of 81659421 is 12495618.

It is not a de Polignac number, because 81659421 - 2⁹ = 81658909 is a prime.

It is a super-3 number, since 3×81659421³ (a number of 25 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81659429) 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, 24946 + ... + 28028.

It is an arithmetic number, because the mean of its divisors is an integer number (5145140).

Almost surely, 2^81659421 is an apocalyptic number.

81659421 is a gapful number since it is divisible by the number (81) formed by its first and last digit.

It is an amenable number.

81659421 is a deficient number, since it is larger than the sum of its proper divisors (41823939).

81659421 is a wasteful number, since it uses less digits than its factorization.

81659421 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3207 (or 3195 counting only the distinct ones).

The product of its digits is 17280, while the sum is 36.

The square root of 81659421 is about 9036.5602415964. The cubic root of 81659421 is about 433.8458345882.

The spelling of 81659421 in words is "eighty-one million, six hundred fifty-nine thousand, four hundred twenty-one".