21555630 has 48 divisors (see below), whose sum is σ = 57114720. Its totient is φ = 5638464.

The previous prime is 21555607. The next prime is 21555637. The reversal of 21555630 is 3655512.

21555630 is a `hidden beast` number, since 21 + 5 + 5 + 5 + 630 = 666.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 21555594 and 21555603.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21555637) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 2511 + ... + 7029.

It is an arithmetic number, because the mean of its divisors is an integer number (1189890).

Almost surely, 2^21555630 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21555630, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28557360).

21555630 is an abundant number, since it is smaller than the sum of its proper divisors (35559090).

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

21555630 is a wasteful number, since it uses less digits than its factorization.

21555630 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4585 (or 4582 counting only the distinct ones).

The product of its (nonzero) digits is 4500, while the sum is 27.

The square root of 21555630 is about 4642.8041095872. The cubic root of 21555630 is about 278.3045073553.

The spelling of 21555630 in words is "twenty-one million, five hundred fifty-five thousand, six hundred thirty".