81733644 has 96 divisors (see below), whose sum is σ = 219340800. Its totient is φ = 26308800.

The previous prime is 81733633. The next prime is 81733657. The reversal of 81733644 is 44633718.

81733644 is a `hidden beast` number, since 8 + 1 + 7 + 3 + 3 + 644 = 666.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a junction number, because it is equal to n+sod(n) for n = 81733599 and 81733608.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 643509 + ... + 643635.

It is an arithmetic number, because the mean of its divisors is an integer number (2284800).

Almost surely, 2^81733644 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 81733644, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (109670400).

81733644 is an abundant number, since it is smaller than the sum of its proper divisors (137607156).

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

81733644 is a wasteful number, since it uses less digits than its factorization.

81733644 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 300 (or 292 counting only the distinct ones).

The product of its digits is 48384, while the sum is 36.

The square root of 81733644 is about 9040.6661259002. Note that the first 3 decimals coincide. The cubic root of 81733644 is about 433.9772404836.

The spelling of 81733644 in words is "eighty-one million, seven hundred thirty-three thousand, six hundred forty-four".