81394579537920 has 1400 divisors, whose sum is σ = 322153139241072. Its totient is φ = 19732019281920.

The previous prime is 81394579537897. The next prime is 81394579537927. The reversal of 81394579537920 is 2973597549318.

81394579537920 is a `hidden beast` number, since 8 + 1 + 39 + 4 + 57 + 9 + 537 + 9 + 2 + 0 = 666.

It is a Harshad number since it is a multiple of its sum of digits (72).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81394579537927) by changing a digit.

It is a polite number, since it can be written in 55 ways as a sum of consecutive naturals, for example, 7399507230715 + ... + 7399507230725.

Almost surely, 2^{81394579537920} is an apocalyptic number.

81394579537920 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 81394579537920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (161076569620536).

81394579537920 is an abundant number, since it is smaller than the sum of its proper divisors (240758559703152).

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

81394579537920 is an frugal number, since it uses more digits than its factorization.

81394579537920 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 104 (or 21 counting only the distinct ones).

The product of its (nonzero) digits is 514382400, while the sum is 72.

The spelling of 81394579537920 in words is "eighty-one trillion, three hundred ninety-four billion, five hundred seventy-nine million, five hundred thirty-seven thousand, nine hundred twenty".