81220742456 has 64 divisors (see below), whose sum is σ = 176462361600. Its totient is φ = 34326384768.

The previous prime is 81220742387. The next prime is 81220742459. The reversal of 81220742456 is 65424702218.

It is a happy number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81220742459) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 3762911 + ... + 3784433.

It is an arithmetic number, because the mean of its divisors is an integer number (2757224400).

Almost surely, 2^81220742456 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 81220742456, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (88231180800).

81220742456 is an abundant number, since it is smaller than the sum of its proper divisors (95241619144).

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

81220742456 is a wasteful number, since it uses less digits than its factorization.

81220742456 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 22468 (or 22464 counting only the distinct ones).

The product of its (nonzero) digits is 215040, while the sum is 41.

The spelling of 81220742456 in words is "eighty-one billion, two hundred twenty million, seven hundred forty-two thousand, four hundred fifty-six".