81605628 has 72 divisors (see below), whose sum is σ = 224060928. Its totient is φ = 24893568.

The previous prime is 81605603. The next prime is 81605647. The reversal of 81605628 is 82650618.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a junction number, because it is equal to n+sod(n) for n = 81605592 and 81605601.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 58750 + ... + 60122.

Almost surely, 2^81605628 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 81605628, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (112030464).

81605628 is an abundant number, since it is smaller than the sum of its proper divisors (142455300).

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

81605628 is a wasteful number, since it uses less digits than its factorization.

81605628 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1523 (or 1518 counting only the distinct ones).

The product of its (nonzero) digits is 23040, while the sum is 36.

The square root of 81605628 is about 9033.5833421738. The cubic root of 81605628 is about 433.7505486017.

The spelling of 81605628 in words is "eighty-one million, six hundred five thousand, six hundred twenty-eight".