81381974240 has 96 divisors (see below), whose sum is σ = 220297371840. Its totient is φ = 27830513664.

The previous prime is 81381974213. The next prime is 81381974251. The reversal of 81381974240 is 4247918318.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 342284 + ... + 529076.

It is an arithmetic number, because the mean of its divisors is an integer number (2294764290).

Almost surely, 2^81381974240 is an apocalyptic number.

81381974240 is a gapful number since it is divisible by the number (80) 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 81381974240, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (110148685920).

81381974240 is an abundant number, since it is smaller than the sum of its proper divisors (138915397600).

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

81381974240 is a wasteful number, since it uses less digits than its factorization.

81381974240 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 187204 (or 187196 counting only the distinct ones).

The product of its (nonzero) digits is 387072, while the sum is 47.

The spelling of 81381974240 in words is "eighty-one billion, three hundred eighty-one million, nine hundred seventy-four thousand, two hundred forty".