81334721 has 8 divisors (see below), whose sum is σ = 87674664. Its totient is φ = 75006720.

The previous prime is 81334709. The next prime is 81334723. The reversal of 81334721 is 12743318.

It can be written as a sum of positive squares in 4 ways, for example, as 4579600 + 76755121 = 2140^2 + 8761^2 .

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 81334721 - 2⁶ = 81334657 is a prime.

It is a super-3 number, since 3×81334721³ (a number of 25 digits) contains 333 as substring.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (81334723) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 15395 + ... + 19991.

It is an arithmetic number, because the mean of its divisors is an integer number (10959333).

Almost surely, 2^81334721 is an apocalyptic number.

It is an amenable number.

81334721 is a deficient number, since it is larger than the sum of its proper divisors (6339943).

81334721 is a wasteful number, since it uses less digits than its factorization.

81334721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5971.

The product of its digits is 4032, while the sum is 29.

The square root of 81334721 is about 9018.5764397714. The cubic root of 81334721 is about 433.2700411834.

The spelling of 81334721 in words is "eighty-one million, three hundred thirty-four thousand, seven hundred twenty-one".