81126720 has 168 divisors, whose sum is σ = 295634664. Its totient is φ = 20348928.

The previous prime is 81126709. The next prime is 81126733. The reversal of 81126720 is 2762118.

It can be written as a sum of positive squares in 4 ways, for example, as 10969344 + 70157376 = 3312^2 + 8376^2 .

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 48132 + ... + 49788.

Almost surely, 2^81126720 is an apocalyptic number.

81126720 is a gapful number since it is divisible by the number (80) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81126720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (147817332).

81126720 is an abundant number, since it is smaller than the sum of its proper divisors (214507944).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

81126720 is a wasteful number, since it uses less digits than its factorization.

81126720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1697 (or 1684 counting only the distinct ones).

The product of its (nonzero) digits is 1344, while the sum is 27.

The square root of 81126720 is about 9007.0372487295. The cubic root of 81126720 is about 432.9003854643.

Adding to 81126720 its reverse (2762118), we get a palindrome (83888838).

The spelling of 81126720 in words is "eighty-one million, one hundred twenty-six thousand, seven hundred twenty".