21252504 has 128 divisors (see below), whose sum is σ = 67415040. Its totient is φ = 5432832.

The previous prime is 21252503. The next prime is 21252509. The reversal of 21252504 is 40525212.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (21).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21252503) 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, 80677 + ... + 80939.

It is an arithmetic number, because the mean of its divisors is an integer number (526680).

Almost surely, 2^21252504 is an apocalyptic number.

21252504 is a gapful number since it is divisible by the number (24) 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 21252504, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33707520).

21252504 is an abundant number, since it is smaller than the sum of its proper divisors (46162536).

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

21252504 is a wasteful number, since it uses less digits than its factorization.

21252504 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 329 (or 325 counting only the distinct ones).

The product of its (nonzero) digits is 800, while the sum is 21.

The square root of 21252504 is about 4610.0438175792. The cubic root of 21252504 is about 276.9937918648.

Adding to 21252504 its reverse (40525212), we get a palindrome (61777716).

The spelling of 21252504 in words is "twenty-one million, two hundred fifty-two thousand, five hundred four".