81385471440 has 320 divisors, whose sum is σ = 345019584000. Its totient is φ = 17171398656.

The previous prime is 81385471429. The next prime is 81385471487. The reversal of 81385471440 is 4417458318.

81385471440 is a `hidden beast` number, since 8 + 138 + 5 + 4 + 71 + 440 = 666.

It is a super-2 number, since 2×81385471440² (a number of 23 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 10465 + ... + 403584.

It is an arithmetic number, because the mean of its divisors is an integer number (1078186200).

Almost surely, 2^81385471440 is an apocalyptic number.

81385471440 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 81385471440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (172509792000).

81385471440 is an abundant number, since it is smaller than the sum of its proper divisors (263634112560).

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

81385471440 is a wasteful number, since it uses less digits than its factorization.

81385471440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 414091 (or 414079 counting only the distinct ones).

The product of its (nonzero) digits is 430080, while the sum is 45.

The spelling of 81385471440 in words is "eighty-one billion, three hundred eighty-five million, four hundred seventy-one thousand, four hundred forty".