81437728 has 12 divisors (see below), whose sum is σ = 160330590. Its totient is φ = 40718848.

The previous prime is 81437693. The next prime is 81437729. The reversal of 81437728 is 82773418.

It can be written as a sum of positive squares in only one way, i.e., 73753744 + 7683984 = 8588^2 + 2772^2 .

It is not an unprimeable number, because it can be changed into a prime (81437729) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1272433 + ... + 1272496.

Almost surely, 2^81437728 is an apocalyptic number.

It is an amenable number.

81437728 is a deficient number, since it is larger than the sum of its proper divisors (78892862).

81437728 is a wasteful number, since it uses less digits than its factorization.

81437728 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2544939 (or 2544931 counting only the distinct ones).

The product of its digits is 75264, while the sum is 40.

The square root of 81437728 is about 9024.2854564780. The cubic root of 81437728 is about 433.4528701123.

The spelling of 81437728 in words is "eighty-one million, four hundred thirty-seven thousand, seven hundred twenty-eight".