21252006 has 48 divisors (see below), whose sum is σ = 49140000. Its totient is φ = 6614784.

The previous prime is 21252001. The next prime is 21252017. The reversal of 21252006 is 60025212.

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

It is a self number, because there is not a number n which added to its sum of digits gives 21252006.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21252001) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 60720 + ... + 61068.

It is an arithmetic number, because the mean of its divisors is an integer number (1023750).

Almost surely, 2^21252006 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21252006, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24570000).

21252006 is an abundant number, since it is smaller than the sum of its proper divisors (27887994).

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

21252006 is a wasteful number, since it uses less digits than its factorization.

21252006 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 573 (or 570 counting only the distinct ones).

The product of its (nonzero) digits is 240, while the sum is 18.

The square root of 21252006 is about 4609.9898047610. The cubic root of 21252006 is about 276.9916282925.

Adding to 21252006 its reverse (60025212), we get a palindrome (81277218).

The spelling of 21252006 in words is "twenty-one million, two hundred fifty-two thousand, six".