81023721 has 8 divisors (see below), whose sum is σ = 108088320. Its totient is φ = 53987472.

The previous prime is 81023713. The next prime is 81023729. The reversal of 81023721 is 12732018.

It is an interprime number because it is at equal distance from previous prime (81023713) and next prime (81023729).

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

It is not a de Polignac number, because 81023721 - 2³ = 81023713 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 81023691 and 81023700.

It is not an unprimeable number, because it can be changed into a prime (81023729) 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, 856 + ... + 12758.

It is an arithmetic number, because the mean of its divisors is an integer number (13511040).

Almost surely, 2^81023721 is an apocalyptic number.

It is an amenable number.

81023721 is a deficient number, since it is larger than the sum of its proper divisors (27064599).

81023721 is a wasteful number, since it uses less digits than its factorization.

81023721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 14175.

The product of its (nonzero) digits is 672, while the sum is 24.

The square root of 81023721 is about 9001.3177368650. The cubic root of 81023721 is about 432.7171035156.

Adding to 81023721 its reverse (12732018), we get a palindrome (93755739).

It can be divided in two parts, 810 and 23721, that added together give a triangular number (24531 = T₂₂₁).

The spelling of 81023721 in words is "eighty-one million, twenty-three thousand, seven hundred twenty-one".