81321724 has 12 divisors (see below), whose sum is σ = 155250648. Its totient is φ = 36964400.

The previous prime is 81321697. The next prime is 81321743. The reversal of 81321724 is 42712318.

It is a super-2 number, since 2×81321724² = 13226445588664352, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 81321692 and 81321701.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 924067 + ... + 924154.

It is an arithmetic number, because the mean of its divisors is an integer number (12937554).

Almost surely, 2^81321724 is an apocalyptic number.

It is an amenable number.

81321724 is a deficient number, since it is larger than the sum of its proper divisors (73928924).

81321724 is a wasteful number, since it uses less digits than its factorization.

81321724 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1848236 (or 1848234 counting only the distinct ones).

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

The square root of 81321724 is about 9017.8558427156. The cubic root of 81321724 is about 433.2469616153.

The spelling of 81321724 in words is "eighty-one million, three hundred twenty-one thousand, seven hundred twenty-four".