81509440320 has 896 divisors, whose sum is σ = 379641323520. Its totient is φ = 15938519040.

The previous prime is 81509440319. The next prime is 81509440321. The reversal of 81509440320 is 2304490518.

81509440320 is a `hidden beast` number, since 81 + 509 + 4 + 40 + 32 + 0 = 666.

It is an interprime number because it is at equal distance from previous prime (81509440319) and next prime (81509440321).

It is a super-2 number, since 2×81509440320² (a number of 23 digits) contains 22 as substring.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81509440321) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 127 ways as a sum of consecutive naturals, for example, 11306157 + ... + 11313363.

Almost surely, 2^81509440320 is an apocalyptic number.

81509440320 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 81509440320, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (189820661760).

81509440320 is an abundant number, since it is smaller than the sum of its proper divisors (298131883200).

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

81509440320 is a wasteful number, since it uses less digits than its factorization.

81509440320 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7268 (or 7252 counting only the distinct ones).

The product of its (nonzero) digits is 34560, while the sum is 36.

The spelling of 81509440320 in words is "eighty-one billion, five hundred nine million, four hundred forty thousand, three hundred twenty".