81443840 has 44 divisors (see below), whose sum is σ = 195382056. Its totient is φ = 32575488.

The previous prime is 81443827. The next prime is 81443867. The reversal of 81443840 is 4834418.

It is a Harshad number since it is a multiple of its sum of digits (32).

It is a junction number, because it is equal to n+sod(n) for n = 81443797 and 81443806.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2834 + ... + 13073.

Almost surely, 2^81443840 is an apocalyptic number.

81443840 is a gapful number since it is divisible by the number (80) formed by its first and last digit.

It is an amenable number.

81443840 is an abundant number, since it is smaller than the sum of its proper divisors (113938216).

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

81443840 is a wasteful number, since it uses less digits than its factorization.

81443840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15932 (or 15914 counting only the distinct ones).

The product of its (nonzero) digits is 12288, while the sum is 32.

The square root of 81443840 is about 9024.6240918944. The cubic root of 81443840 is about 433.4637135618.

The spelling of 81443840 in words is "eighty-one million, four hundred forty-three thousand, eight hundred forty".