81266540544 has 408 divisors, whose sum is σ = 278625488960. Its totient is φ = 23219011584.

The previous prime is 81266540503. The next prime is 81266540617. The reversal of 81266540544 is 44504566218.

It is a happy number.

81266540544 is a `hidden beast` number, since 8 + 1 + 2 + 6 + 65 + 40 + 544 = 666.

It is a super-2 number, since 2×81266540544² (a number of 23 digits) contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 81266540544.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 11609505789 + ... + 11609505795.

Almost surely, 2^81266540544 is an apocalyptic number.

81266540544 is a gapful number since it is divisible by the number (84) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81266540544, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (139312744480).

81266540544 is an abundant number, since it is smaller than the sum of its proper divisors (197358948416).

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

81266540544 is an frugal number, since it uses more digits than its factorization.

81266540544 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 72 (or 12 counting only the distinct ones).

The product of its (nonzero) digits is 921600, while the sum is 45.

The spelling of 81266540544 in words is "eighty-one billion, two hundred sixty-six million, five hundred forty thousand, five hundred forty-four".