21223260 has 72 divisors (see below), whose sum is σ = 64873536. Its totient is φ = 5616000.

The previous prime is 21223219. The next prime is 21223261. The reversal of 21223260 is 6232212.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21223261) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 27885 + ... + 28635.

Almost surely, 2^21223260 is an apocalyptic number.

21223260 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 21223260, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32436768).

21223260 is an abundant number, since it is smaller than the sum of its proper divisors (43650276).

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

21223260 is a wasteful number, since it uses less digits than its factorization.

21223260 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 923 (or 918 counting only the distinct ones).

The product of its (nonzero) digits is 288, while the sum is 18.

The square root of 21223260 is about 4606.8709554317. The cubic root of 21223260 is about 276.8666833172.

Adding to 21223260 its reverse (6232212), we get a palindrome (27455472).

The spelling of 21223260 in words is "twenty-one million, two hundred twenty-three thousand, two hundred sixty".