81131722012 has 48 divisors (see below), whose sum is σ = 164141655552. Its totient is φ = 34678542080.

The previous prime is 81131721977. The next prime is 81131722043. The reversal of 81131722012 is 21022713118.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 823293 + ... + 916555.

It is an arithmetic number, because the mean of its divisors is an integer number (3419617824).

Almost surely, 2^81131722012 is an apocalyptic number.

It is an amenable number.

81131722012 is an abundant number, since it is smaller than the sum of its proper divisors (83009933540).

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

81131722012 is a wasteful number, since it uses less digits than its factorization.

81131722012 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 94458 (or 94456 counting only the distinct ones).

The product of its (nonzero) digits is 1344, while the sum is 28.

The spelling of 81131722012 in words is "eighty-one billion, one hundred thirty-one million, seven hundred twenty-two thousand, twelve".