81720432 has 60 divisors (see below), whose sum is σ = 231953904. Its totient is φ = 26853120.

The previous prime is 81720427. The next prime is 81720437. The reversal of 81720432 is 23402718.

It is an interprime number because it is at equal distance from previous prime (81720427) and next prime (81720437).

It is a junction number, because it is equal to n+sod(n) for n = 81720396 and 81720405.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81720437) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 6228 + ... + 14220.

Almost surely, 2^81720432 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 81720432, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (115976952).

81720432 is an abundant number, since it is smaller than the sum of its proper divisors (150233472).

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

81720432 is a wasteful number, since it uses less digits than its factorization.

81720432 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8078 (or 8069 counting only the distinct ones).

The product of its (nonzero) digits is 2688, while the sum is 27.

The square root of 81720432 is about 9039.9353979993. The cubic root of 81720432 is about 433.9538555143.

The spelling of 81720432 in words is "eighty-one million, seven hundred twenty thousand, four hundred thirty-two".