21225660 has 96 divisors (see below), whose sum is σ = 64162560. Its totient is φ = 5225472.

The previous prime is 21225653. The next prime is 21225661. The reversal of 21225660 is 6652212.

It is a self number, because there is not a number n which added to its sum of digits gives 21225660.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21225661) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 48804 + ... + 49236.

It is an arithmetic number, because the mean of its divisors is an integer number (668360).

Almost surely, 2^21225660 is an apocalyptic number.

21225660 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 21225660, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32081280).

21225660 is an abundant number, since it is smaller than the sum of its proper divisors (42936900).

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

21225660 is a wasteful number, since it uses less digits than its factorization.

21225660 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 507 (or 505 counting only the distinct ones).

The product of its (nonzero) digits is 1440, while the sum is 24.

The square root of 21225660 is about 4607.1314285573. The cubic root of 21225660 is about 276.8771192727.

Adding to 21225660 its reverse (6652212), we get a palindrome (27877872).

The spelling of 21225660 in words is "twenty-one million, two hundred twenty-five thousand, six hundred sixty".