81239824 has 10 divisors (see below), whose sum is σ = 157402190. Its totient is φ = 40619904.

The previous prime is 81239813. The next prime is 81239843. The reversal of 81239824 is 42893218.

81239824 = 872² + 873² + ... + 967².

It can be written as a sum of positive squares in only one way, i.e., 70560000 + 10679824 = 8400^2 + 3268^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2538729 + ... + 2538760.

It is an arithmetic number, because the mean of its divisors is an integer number (15740219).

Almost surely, 2^81239824 is an apocalyptic number.

It is an amenable number.

81239824 is a deficient number, since it is larger than the sum of its proper divisors (76162366).

81239824 is a wasteful number, since it uses less digits than its factorization.

81239824 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5077497 (or 5077491 counting only the distinct ones).

The product of its digits is 27648, while the sum is 37.

The square root of 81239824 is about 9013.3137080654. The cubic root of 81239824 is about 433.1014701737.

The spelling of 81239824 in words is "eighty-one million, two hundred thirty-nine thousand, eight hundred twenty-four".