81709824 has 72 divisors (see below), whose sum is σ = 248550400. Its totient is φ = 23344128.

The previous prime is 81709819. The next prime is 81709877. The reversal of 81709824 is 42890718.

It is a super-2 number, since 2×81709824² = 13352990676221952, which contains 22 as substring.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2224 + ... + 12975.

Almost surely, 2^81709824 is an apocalyptic number.

81709824 is a gapful number since it is divisible by the number (84) 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 81709824, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (124275200).

81709824 is an abundant number, since it is smaller than the sum of its proper divisors (166840576).

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

81709824 is a wasteful number, since it uses less digits than its factorization.

81709824 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 15225 (or 15211 counting only the distinct ones).

The product of its (nonzero) digits is 32256, while the sum is 39.

The square root of 81709824 is about 9039.3486491008. The cubic root of 81709824 is about 433.9350777472.

The spelling of 81709824 in words is "eighty-one million, seven hundred nine thousand, eight hundred twenty-four".