81191020 has 24 divisors (see below), whose sum is σ = 170755200. Its totient is φ = 32428032.

The previous prime is 81191017. The next prime is 81191023. The reversal of 81191020 is 2019118.

It is an interprime number because it is at equal distance from previous prime (81191017) and next prime (81191023).

It is a junction number, because it is equal to n+sod(n) for n = 81190982 and 81191000.

It is not an unprimeable number, because it can be changed into a prime (81191023) 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 7 ways as a sum of consecutive naturals, for example, 12741 + ... + 18019.

It is an arithmetic number, because the mean of its divisors is an integer number (7114800).

Almost surely, 2^81191020 is an apocalyptic number.

It is an amenable number.

81191020 is an abundant number, since it is smaller than the sum of its proper divisors (89564180).

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

81191020 is a wasteful number, since it uses less digits than its factorization.

81191020 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6057 (or 6055 counting only the distinct ones).

The product of its (nonzero) digits is 144, while the sum is 22.

The square root of 81191020 is about 9010.6059729632. The cubic root of 81191020 is about 433.0147256965.

The spelling of 81191020 in words is "eighty-one million, one hundred ninety-one thousand, twenty".