81231724 has 48 divisors (see below), whose sum is σ = 168920640. Its totient is φ = 33454080.

The previous prime is 81231679. The next prime is 81231737. The reversal of 81231724 is 42713218.

It is a Harshad number since it is a multiple of its sum of digits (28).

It is a junction number, because it is equal to n+sod(n) for n = 81231692 and 81231701.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 91764 + ... + 92644.

It is an arithmetic number, because the mean of its divisors is an integer number (3519180).

Almost surely, 2^81231724 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 81231724, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (84460320).

81231724 is an abundant number, since it is smaller than the sum of its proper divisors (87688916).

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

81231724 is a wasteful number, since it uses less digits than its factorization.

81231724 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1018 (or 1016 counting only the distinct ones).

The product of its digits is 2688, while the sum is 28.

The square root of 81231724 is about 9012.8643615667. The cubic root of 81231724 is about 433.0870755975.

The spelling of 81231724 in words is "eighty-one million, two hundred thirty-one thousand, seven hundred twenty-four".