81620928 has 168 divisors, whose sum is σ = 250582176. Its totient is φ = 25344000.

The previous prime is 81620911. The next prime is 81620947. The reversal of 81620928 is 82902618.

81620928 is a `hidden beast` number, since 8 + 1 + 620 + 9 + 28 = 666.

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 = 81620892 and 81620901.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 808078 + ... + 808178.

Almost surely, 2^81620928 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 81620928, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (125291088).

81620928 is an abundant number, since it is smaller than the sum of its proper divisors (168961248).

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

81620928 is a wasteful number, since it uses less digits than its factorization.

81620928 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 203 (or 190 counting only the distinct ones).

The product of its (nonzero) digits is 13824, while the sum is 36.

The square root of 81620928 is about 9034.4301425159. The cubic root of 81620928 is about 433.7776544474. Note that the first 3 decimals are identical.

The spelling of 81620928 in words is "eighty-one million, six hundred twenty thousand, nine hundred twenty-eight".