81347563520 has 78 divisors (see below), whose sum is σ = 195308317278. Its totient is φ = 32522698752.

The previous prime is 81347563519. The next prime is 81347563523. The reversal of 81347563520 is 2536574318.

It can be written as a sum of positive squares in 3 ways, for example, as 23162404864 + 58185158656 = 152192^2 + 241216^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81347563523) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 40815644 + ... + 40817636.

Almost surely, 2^81347563520 is an apocalyptic number.

81347563520 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 81347563520, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (97654158639).

81347563520 is an abundant number, since it is smaller than the sum of its proper divisors (113960753758).

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

81347563520 is an frugal number, since it uses more digits than its factorization.

81347563520 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4015 (or 2000 counting only the distinct ones).

The product of its (nonzero) digits is 604800, while the sum is 44.

The spelling of 81347563520 in words is "eighty-one billion, three hundred forty-seven million, five hundred sixty-three thousand, five hundred twenty".