81787272 has 96 divisors (see below), whose sum is σ = 251903520. Its totient is φ = 21987840.

The previous prime is 81787217. The next prime is 81787273. The reversal of 81787272 is 27278718.

It is a super-2 number, since 2×81787272² = 13378315722403968, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (42).

It is a nude number because it is divisible by every one of its digits.

It is not an unprimeable number, because it can be changed into a prime (81787273) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 17947 + ... + 22037.

It is an arithmetic number, because the mean of its divisors is an integer number (2623995).

Almost surely, 2^81787272 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 81787272, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (125951760).

81787272 is an abundant number, since it is smaller than the sum of its proper divisors (170116248).

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

81787272 is a wasteful number, since it uses less digits than its factorization.

81787272 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4131 (or 4120 counting only the distinct ones).

The product of its digits is 87808, while the sum is 42.

The square root of 81787272 is about 9043.6315714430. The cubic root of 81787272 is about 434.0721350788.

The spelling of 81787272 in words is "eighty-one million, seven hundred eighty-seven thousand, two hundred seventy-two".