81443556 has 60 divisors (see below), whose sum is σ = 214287612. Its totient is φ = 26972352.

The previous prime is 81443497. The next prime is 81443561. The reversal of 81443556 is 65534418.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 77158656 + 4284900 = 8784^2 + 2070^2 .

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a self number, because there is not a number n which added to its sum of digits gives 81443556.

It is an unprimeable number.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 55326 + ... + 56778.

Almost surely, 2^81443556 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 81443556, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (107143806).

81443556 is an abundant number, since it is smaller than the sum of its proper divisors (132844056).

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

81443556 is a wasteful number, since it uses less digits than its factorization.

81443556 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1642 (or 1631 counting only the distinct ones).

The product of its digits is 57600, while the sum is 36.

The square root of 81443556 is about 9024.6083571532. The cubic root of 81443556 is about 433.4632097224.

It can be divided in two parts, 81 and 443556, that multiplied together give a square (35928036 = 5994²).

The spelling of 81443556 in words is "eighty-one million, four hundred forty-three thousand, five hundred fifty-six".