81255636 has 120 divisors (see below), whose sum is σ = 264914496. Its totient is φ = 21098880.

The previous prime is 81255583. The next prime is 81255637. The reversal of 81255636 is 63655218.

81255636 is a `hidden beast` number, since 8 + 12 + 5 + 5 + 636 = 666.

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 81255636.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81255637) by changing a digit.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 23320 + ... + 26576.

Almost surely, 2^81255636 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 81255636, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (132457248).

81255636 is an abundant number, since it is smaller than the sum of its proper divisors (183658860).

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

81255636 is a wasteful number, since it uses less digits than its factorization.

81255636 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3291 (or 3280 counting only the distinct ones).

The product of its digits is 43200, while the sum is 36.

The square root of 81255636 is about 9014.1908122693. The cubic root of 81255636 is about 433.1295670514.

The spelling of 81255636 in words is "eighty-one million, two hundred fifty-five thousand, six hundred thirty-six".