81145591020 has 960 divisors, whose sum is σ = 311457484800. Its totient is φ = 17468006400.

The previous prime is 81145591019. The next prime is 81145591049. The reversal of 81145591020 is 2019554118.

81145591020 is a `hidden beast` number, since 8 + 1 + 1 + 45 + 591 + 0 + 20 = 666.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is an unprimeable number.

It is a polite number, since it can be written in 319 ways as a sum of consecutive naturals, for example, 537387945 + ... + 537388095.

It is an arithmetic number, because the mean of its divisors is an integer number (324434880).

Almost surely, 2^81145591020 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81145591020, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (155728742400).

81145591020 is an abundant number, since it is smaller than the sum of its proper divisors (230311893780).

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

81145591020 is a wasteful number, since it uses less digits than its factorization.

81145591020 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 300 (or 289 counting only the distinct ones).

The product of its (nonzero) digits is 14400, while the sum is 36.

The spelling of 81145591020 in words is "eighty-one billion, one hundred forty-five million, five hundred ninety-one thousand, twenty".