81177642728 has 128 divisors (see below), whose sum is σ = 202523462400. Its totient is φ = 29601552384.

The previous prime is 81177642727. The next prime is 81177642731. The reversal of 81177642728 is 82724677118.

It is a super-2 number, since 2×81177642728² (a number of 23 digits) contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 81177642728.

It is not an unprimeable number, because it can be changed into a prime (81177642727) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 432476 + ... + 591092.

It is an arithmetic number, because the mean of its divisors is an integer number (1582214550).

Almost surely, 2^81177642728 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 81177642728, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (101261731200).

81177642728 is an abundant number, since it is smaller than the sum of its proper divisors (121345819672).

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

81177642728 is a wasteful number, since it uses less digits than its factorization.

81177642728 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 158699 (or 158695 counting only the distinct ones).

The product of its digits is 2107392, while the sum is 53.

The spelling of 81177642728 in words is "eighty-one billion, one hundred seventy-seven million, six hundred forty-two thousand, seven hundred twenty-eight".