81494864640 has 360 divisors, whose sum is σ = 333264143520. Its totient is φ = 18627231744.

The previous prime is 81494864623. The next prime is 81494864641. The reversal of 81494864640 is 4646849418.

81494864640 is a `hidden beast` number, since 8 + 14 + 94 + 86 + 464 + 0 = 666.

It is a tau number, because it is divible by the number of its divisors (360).

It is a Harshad number since it is a multiple of its sum of digits (54).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81494864641) by changing a digit.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 669616 + ... + 781904.

It is an arithmetic number, because the mean of its divisors is an integer number (925733732).

Almost surely, 2^81494864640 is an apocalyptic number.

81494864640 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 81494864640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (166632071760).

81494864640 is an abundant number, since it is smaller than the sum of its proper divisors (251769278880).

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

81494864640 is a wasteful number, since it uses less digits than its factorization.

81494864640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 112329 (or 112306 counting only the distinct ones).

The product of its (nonzero) digits is 5308416, while the sum is 54.

The spelling of 81494864640 in words is "eighty-one billion, four hundred ninety-four million, eight hundred sixty-four thousand, six hundred forty".