21505552 has 20 divisors (see below), whose sum is σ = 43479360. Its totient is φ = 10285088.

The previous prime is 21505543. The next prime is 21505637. The reversal of 21505552 is 25550512.

It is a happy number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 28852 + ... + 29587.

It is an arithmetic number, because the mean of its divisors is an integer number (2173968).

Almost surely, 2^21505552 is an apocalyptic number.

It is an amenable number.

21505552 is an abundant number, since it is smaller than the sum of its proper divisors (21973808).

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

21505552 is a wasteful number, since it uses less digits than its factorization.

21505552 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 58470 (or 58464 counting only the distinct ones).

The product of its (nonzero) digits is 2500, while the sum is 25.

The square root of 21505552 is about 4637.4078966595. The cubic root of 21505552 is about 278.0888214019.

The spelling of 21505552 in words is "twenty-one million, five hundred five thousand, five hundred fifty-two".