81817481 has 8 divisors (see below), whose sum is σ = 86770440. Its totient is φ = 76880128.

The previous prime is 81817453. The next prime is 81817487. The reversal of 81817481 is 18471818.

It can be written as a sum of positive squares in 4 ways, for example, as 33640000 + 48177481 = 5800^2 + 6941^2 .

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

It is a cyclic number.

It is not a de Polignac number, because 81817481 - 2¹⁰ = 81816457 is a prime.

It is a super-2 number, since 2×81817481² = 13388200394370722, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81817487) 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 7 ways as a sum of consecutive naturals, for example, 7955 + ... + 15063.

It is an arithmetic number, because the mean of its divisors is an integer number (10846305).

Almost surely, 2^81817481 is an apocalyptic number.

It is an amenable number.

81817481 is a deficient number, since it is larger than the sum of its proper divisors (4952959).

81817481 is a wasteful number, since it uses less digits than its factorization.

81817481 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7803.

The product of its digits is 14336, while the sum is 38.

The square root of 81817481 is about 9045.3015980674. The cubic root of 81817481 is about 434.1255715556.

The spelling of 81817481 in words is "eighty-one million, eight hundred seventeen thousand, four hundred eighty-one".