81000532720 has 40 divisors (see below), whose sum is σ = 189525798144. Its totient is φ = 32193837312.

The previous prime is 81000532667. The next prime is 81000532729. The reversal of 81000532720 is 2723500018.

It is a tau number, because it is divible by the number of its divisors (40).

It is a super-2 number, since 2×81000532720² (a number of 23 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81000532729) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3211984 + ... + 3237103.

Almost surely, 2^81000532720 is an apocalyptic number.

81000532720 is a gapful number since it is divisible by the number (80) formed by its first and last digit.

It is an amenable number.

81000532720 is an abundant number, since it is smaller than the sum of its proper divisors (108525265424).

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

81000532720 is a wasteful number, since it uses less digits than its factorization.

81000532720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6449257 (or 6449251 counting only the distinct ones).

The product of its (nonzero) digits is 3360, while the sum is 28.

The spelling of 81000532720 in words is "eighty-one billion, five hundred thirty-two thousand, seven hundred twenty".