21705552 has 120 divisors (see below), whose sum is σ = 67549248. Its totient is φ = 6451200.

The previous prime is 21705547. The next prime is 21705553. The reversal of 21705552 is 25550712.

It is a happy number.

It is a super-2 number, since 2×21705552² = 942261975249408, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21705553) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 112368 + ... + 112560.

Almost surely, 2^21705552 is an apocalyptic number.

21705552 is a gapful number since it is divisible by the number (22) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21705552, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33774624).

21705552 is an abundant number, since it is smaller than the sum of its proper divisors (45843696).

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

21705552 is a wasteful number, since it uses less digits than its factorization.

21705552 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 289 (or 280 counting only the distinct ones).

The product of its (nonzero) digits is 3500, while the sum is 27.

The square root of 21705552 is about 4658.9217636702. The cubic root of 21705552 is about 278.9482310392.

The spelling of 21705552 in words is "twenty-one million, seven hundred five thousand, five hundred fifty-two".