81126721 has 8 divisors (see below), whose sum is σ = 90185984. Its totient is φ = 72470160.

The previous prime is 81126709. The next prime is 81126733. The reversal of 81126721 is 12762118.

It is an interprime number because it is at equal distance from previous prime (81126709) and next prime (81126733).

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 81126721 - 2⁹ = 81126209 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 81126721.

It is not an unprimeable number, because it can be changed into a prime (81126701) 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, 100251 + ... + 101056.

It is an arithmetic number, because the mean of its divisors is an integer number (11273248).

Almost surely, 2^81126721 is an apocalyptic number.

It is an amenable number.

81126721 is a deficient number, since it is larger than the sum of its proper divisors (9059263).

81126721 is a wasteful number, since it uses less digits than its factorization.

81126721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 201351.

The product of its digits is 1344, while the sum is 28.

The square root of 81126721 is about 9007.0373042416. The cubic root of 81126721 is about 432.9003872430.

Adding to 81126721 its reverse (12762118), we get a palindrome (93888839).

The spelling of 81126721 in words is "eighty-one million, one hundred twenty-six thousand, seven hundred twenty-one".