81333720 has 160 divisors (see below), whose sum is σ = 294552720. Its totient is φ = 20010240.

The previous prime is 81333691. The next prime is 81333731. The reversal of 81333720 is 2733318.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is an unprimeable number.

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 39 ways as a sum of consecutive naturals, for example, 41155 + ... + 43085.

Almost surely, 2^81333720 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81333720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (147276360).

81333720 is an abundant number, since it is smaller than the sum of its proper divisors (213219000).

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

81333720 is a wasteful number, since it uses less digits than its factorization.

81333720 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1967 (or 1954 counting only the distinct ones).

The product of its (nonzero) digits is 3024, while the sum is 27.

The square root of 81333720 is about 9018.5209430372. The cubic root of 81333720 is about 433.2682637339.

The spelling of 81333720 in words is "eighty-one million, three hundred thirty-three thousand, seven hundred twenty".