21551200 has 144 divisors (see below), whose sum is σ = 59996160. Its totient is φ = 7488000.

The previous prime is 21551177. The next prime is 21551221. The reversal of 21551200 is 215512.

It is a Harshad number since it is a multiple of its sum of digits (16).

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, 272761 + ... + 272839.

It is an arithmetic number, because the mean of its divisors is an integer number (416640).

Almost surely, 2^21551200 is an apocalyptic number.

21551200 is a gapful number since it is divisible by the number (20) 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 21551200, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29998080).

21551200 is an abundant number, since it is smaller than the sum of its proper divisors (38444960).

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

21551200 is a wasteful number, since it uses less digits than its factorization.

21551200 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 141 (or 128 counting only the distinct ones).

The product of its (nonzero) digits is 100, while the sum is 16.

The square root of 21551200 is about 4642.3270027003. The cubic root of 21551200 is about 278.2854408216.

21551200 divided by its product of nonzero digits (100) gives a palindrome (215512).

Adding to 21551200 its reverse (215512), we get a palindrome (21766712).

Multiplying 21551200 by its reverse (215512), we get a square (4644542214400 = 2155120²).

21551200 divided by its reverse (215512) gives a square (100 = 10²).

It can be divided in two parts, 215 and 51200, that added together give a palindrome (51415).

The spelling of 21551200 in words is "twenty-one million, five hundred fifty-one thousand, two hundred".