81917405 has 4 divisors (see below), whose sum is σ = 98300892. Its totient is φ = 65533920.

The previous prime is 81917393. The next prime is 81917447. The reversal of 81917405 is 50471918.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 52606009 + 29311396 = 7253^2 + 5414^2 .

It is not a de Polignac number, because 81917405 - 2⁴ = 81917389 is a prime.

It is a super-2 number, since 2×81917405² = 13420922483868050, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

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 3 ways as a sum of consecutive naturals, for example, 8191736 + ... + 8191745.

It is an arithmetic number, because the mean of its divisors is an integer number (24575223).

Almost surely, 2^81917405 is an apocalyptic number.

It is an amenable number.

81917405 is a deficient number, since it is larger than the sum of its proper divisors (16383487).

81917405 is a wasteful number, since it uses less digits than its factorization.

81917405 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16383486.

The product of its (nonzero) digits is 10080, while the sum is 35.

The square root of 81917405 is about 9050.8234432012. The cubic root of 81917405 is about 434.3022327254.

The spelling of 81917405 in words is "eighty-one million, nine hundred seventeen thousand, four hundred five".