81917409 has 8 divisors (see below), whose sum is σ = 124826560. Its totient is φ = 46809936.

The previous prime is 81917393. The next prime is 81917447. The reversal of 81917409 is 90471918.

It is a happy number.

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

It is not a de Polignac number, because 81917409 - 2⁴ = 81917393 is a prime.

It is a super-3 number, since 3×81917409³ (a number of 25 digits) contains 333 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81917309) 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, 1950394 + ... + 1950435.

It is an arithmetic number, because the mean of its divisors is an integer number (15603320).

Almost surely, 2^81917409 is an apocalyptic number.

It is an amenable number.

81917409 is a deficient number, since it is larger than the sum of its proper divisors (42909151).

81917409 is a wasteful number, since it uses less digits than its factorization.

81917409 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3900839.

The product of its (nonzero) digits is 18144, while the sum is 39.

The square root of 81917409 is about 9050.8236641755. The cubic root of 81917409 is about 434.3022397944.

The spelling of 81917409 in words is "eighty-one million, nine hundred seventeen thousand, four hundred nine".