55621728 has 144 divisors (see below), whose sum is σ = 171714816. Its totient is φ = 17677440.

The previous prime is 55621711. The next prime is 55621733. The reversal of 55621728 is 82712655.

It is a happy number.

55621728 is a `hidden beast` number, since 5 + 5 + 621 + 7 + 28 = 666.

It is a tau number, because it is divible by the number of its divisors (144).

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 = 55621692 and 55621701.

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, 178693 + ... + 179003.

It is an arithmetic number, because the mean of its divisors is an integer number (1192464).

Almost surely, 2^55621728 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 55621728, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (85857408).

55621728 is an abundant number, since it is smaller than the sum of its proper divisors (116093088).

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

55621728 is a wasteful number, since it uses less digits than its factorization.

55621728 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 359 (or 339 counting only the distinct ones).

The product of its digits is 33600, while the sum is 36.

The square root of 55621728 is about 7457.9975864839. The cubic root of 55621728 is about 381.7228511539.

Adding to 55621728 its sum of digits (36), we get a square (55621764 = 7458²).

The spelling of 55621728 in words is "fifty-five million, six hundred twenty-one thousand, seven hundred twenty-eight".