81717381 has 12 divisors (see below), whose sum is σ = 118173900. Its totient is φ = 54414720.

The previous prime is 81717371. The next prime is 81717431. The reversal of 81717381 is 18371718.

It can be written as a sum of positive squares in 2 ways, for example, as 27562500 + 54154881 = 5250^2 + 7359^2 .

It is not a de Polignac number, because 81717381 - 2¹³ = 81709189 is a prime.

It is a super-2 number, since 2×81717381² = 13355460714998322, which contains 22 as substring.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81717371) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 3645 + ... + 13293.

It is an arithmetic number, because the mean of its divisors is an integer number (9847825).

Almost surely, 2^81717381 is an apocalyptic number.

It is an amenable number.

81717381 is a deficient number, since it is larger than the sum of its proper divisors (36456519).

81717381 is a wasteful number, since it uses less digits than its factorization.

81717381 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10596 (or 10593 counting only the distinct ones).

The product of its digits is 9408, while the sum is 36.

The square root of 81717381 is about 9039.7666452182. The cubic root of 81717381 is about 433.9484549485.

The spelling of 81717381 in words is "eighty-one million, seven hundred seventeen thousand, three hundred eighty-one".