21144684 has 48 divisors (see below), whose sum is σ = 55149696. Its totient is φ = 6249600.

The previous prime is 21144679. The next prime is 21144703. The reversal of 21144684 is 48644112.

It is a super-2 number, since 2×21144684² = 894195322919712, which contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 3459 + ... + 7365.

It is an arithmetic number, because the mean of its divisors is an integer number (1148952).

Almost surely, 2^21144684 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21144684, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27574848).

21144684 is an abundant number, since it is smaller than the sum of its proper divisors (34005012).

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

21144684 is a wasteful number, since it uses less digits than its factorization.

21144684 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3966 (or 3964 counting only the distinct ones).

The product of its digits is 6144, while the sum is 30.

The square root of 21144684 is about 4598.3349160321. The cubic root of 21144684 is about 276.5245747031.

Adding to 21144684 its reverse (48644112), we get a palindrome (69788796).

The spelling of 21144684 in words is "twenty-one million, one hundred forty-four thousand, six hundred eighty-four".