21172200 has 144 divisors (see below), whose sum is σ = 76081440. Its totient is φ = 4771200.

The previous prime is 21172189. The next prime is 21172223. The reversal of 21172200 is 227112.

It is a Harshad number since it is a multiple of its sum of digits (15).

It is a self number, because there is not a number n which added to its sum of digits gives 21172200.

It is an unprimeable number.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 298165 + ... + 298235.

Almost surely, 2^21172200 is an apocalyptic number.

21172200 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 21172200, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (38040720).

21172200 is an abundant number, since it is smaller than the sum of its proper divisors (54909240).

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

21172200 is a wasteful number, since it uses less digits than its factorization.

21172200 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 168 (or 88 counting only the distinct ones).

The product of its (nonzero) digits is 56, while the sum is 15.

The square root of 21172200 is about 4601.3258958696. The cubic root of 21172200 is about 276.6444716957.

Adding to 21172200 its reverse (227112), we get a palindrome (21399312).

The spelling of 21172200 in words is "twenty-one million, one hundred seventy-two thousand, two hundred".