81381255012 has 144 divisors (see below), whose sum is σ = 224973315840. Its totient is φ = 25652145312.

The previous prime is 81381255001. The next prime is 81381255013. The reversal of 81381255012 is 21055218318.

81381255012 is a `hidden beast` number, since 8 + 13 + 81 + 2 + 550 + 12 = 666.

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

It is not an unprimeable number, because it can be changed into a prime (81381255013) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 10836963 + ... + 10844469.

Almost surely, 2^81381255012 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 81381255012, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (112486657920).

81381255012 is an abundant number, since it is smaller than the sum of its proper divisors (143592060828).

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

81381255012 is a wasteful number, since it uses less digits than its factorization.

81381255012 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8132 (or 8118 counting only the distinct ones).

The product of its (nonzero) digits is 19200, while the sum is 36.

The spelling of 81381255012 in words is "eighty-one billion, three hundred eighty-one million, two hundred fifty-five thousand, twelve".