81347563521 has 64 divisors (see below), whose sum is σ = 140398479360. Its totient is φ = 45592804800.

The previous prime is 81347563519. The next prime is 81347563523. The reversal of 81347563521 is 12536574318.

It is a happy number.

81347563521 is a `hidden beast` number, since 8 + 1 + 3 + 4 + 7 + 5 + 635 + 2 + 1 = 666.

It is an interprime number because it is at equal distance from previous prime (81347563519) and next prime (81347563523).

It is not a de Polignac number, because 81347563521 - 2¹ = 81347563519 is a prime.

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

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 2022610 + ... + 2062436.

It is an arithmetic number, because the mean of its divisors is an integer number (2193726240).

Almost surely, 2^81347563521 is an apocalyptic number.

It is an amenable number.

81347563521 is a deficient number, since it is larger than the sum of its proper divisors (59050915839).

81347563521 is a wasteful number, since it uses less digits than its factorization.

81347563521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 40051 (or 40045 counting only the distinct ones).

The product of its digits is 604800, while the sum is 45.

The spelling of 81347563521 in words is "eighty-one billion, three hundred forty-seven million, five hundred sixty-three thousand, five hundred twenty-one".