21252280 has 64 divisors (see below), whose sum is σ = 55800000. Its totient is φ = 7281792.

The previous prime is 21252269. The next prime is 21252281. The reversal of 21252280 is 8225212.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21252281) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 12946 + ... + 14494.

It is an arithmetic number, because the mean of its divisors is an integer number (871875).

Almost surely, 2^21252280 is an apocalyptic number.

21252280 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 21252280, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27900000).

21252280 is an abundant number, since it is smaller than the sum of its proper divisors (34547720).

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

21252280 is a wasteful number, since it uses less digits than its factorization.

21252280 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1581 (or 1563 counting only the distinct ones).

The product of its (nonzero) digits is 640, while the sum is 22.

The square root of 21252280 is about 4610.0195227352. The cubic root of 21252280 is about 276.9928186959.

Adding to 21252280 its reverse (8225212), we get a palindrome (29477492).

The spelling of 21252280 in words is "twenty-one million, two hundred fifty-two thousand, two hundred eighty".