81616128 has 72 divisors (see below), whose sum is σ = 236989536. Its totient is φ = 24729600.

The previous prime is 81616127. The next prime is 81616147. The reversal of 81616128 is 82161618.

It is a super-2 number, since 2×81616128² = 13322384699424768, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (33).

It is a nude number because it is divisible by every one of its digits.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81616123) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3618 + ... + 13278.

Almost surely, 2^81616128 is an apocalyptic number.

81616128 is a gapful number since it is divisible by the number (88) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81616128, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (118494768).

81616128 is an abundant number, since it is smaller than the sum of its proper divisors (155373408).

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

81616128 is a wasteful number, since it uses less digits than its factorization.

81616128 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9691 (or 9677 counting only the distinct ones).

The product of its digits is 4608, while the sum is 33.

The square root of 81616128 is about 9034.1644882081. The cubic root of 81616128 is about 433.7691510174.

Subtracting 81616128 from its reverse (82161618), we obtain a triangular number (545490 = T₁₀₄₄).

The spelling of 81616128 in words is "eighty-one million, six hundred sixteen thousand, one hundred twenty-eight".