21609126 has 64 divisors (see below), whose sum is σ = 59880960. Its totient is φ = 5611680.

The previous prime is 21609109. The next prime is 21609131. The reversal of 21609126 is 62190612.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a self number, because there is not a number n which added to its sum of digits gives 21609126.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 1560 + ... + 6756.

It is an arithmetic number, because the mean of its divisors is an integer number (935640).

Almost surely, 2^21609126 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21609126, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29940480).

21609126 is an abundant number, since it is smaller than the sum of its proper divisors (38271834).

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

21609126 is a wasteful number, since it uses less digits than its factorization.

21609126 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5226 (or 5220 counting only the distinct ones).

The product of its (nonzero) digits is 1296, while the sum is 27.

The square root of 21609126 is about 4648.5617130463. The cubic root of 21609126 is about 278.5345459200.

Adding to 21609126 its reverse (62190612), we get a palindrome (83799738).

The spelling of 21609126 in words is "twenty-one million, six hundred nine thousand, one hundred twenty-six".