81281511540 has 144 divisors (see below), whose sum is σ = 248587754688. Its totient is φ = 21496845312.

The previous prime is 81281511539. The next prime is 81281511583. The reversal of 81281511540 is 4511518218.

81281511540 is a `hidden beast` number, since 8 + 12 + 81 + 511 + 54 + 0 = 666.

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

It is a junction number, because it is equal to n+sod(n) for n = 81281511495 and 81281511504.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 15342172 + ... + 15347468.

It is an arithmetic number, because the mean of its divisors is an integer number (1726303852).

Almost surely, 2^81281511540 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 81281511540, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (124293877344).

81281511540 is an abundant number, since it is smaller than the sum of its proper divisors (167306243148).

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

81281511540 is a wasteful number, since it uses less digits than its factorization.

81281511540 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5998 (or 5993 counting only the distinct ones).

The product of its (nonzero) digits is 12800, while the sum is 36.

The spelling of 81281511540 in words is "eighty-one billion, two hundred eighty-one million, five hundred eleven thousand, five hundred forty".