21418644 has 96 divisors (see below), whose sum is σ = 57401344. Its totient is φ = 6168960.

The previous prime is 21418633. The next prime is 21418693. The reversal of 21418644 is 44681412.

It is a congruent number.

It is an unprimeable number.

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 31 ways as a sum of consecutive naturals, for example, 207897 + ... + 207999.

Almost surely, 2^21418644 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 21418644, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28700672).

21418644 is an abundant number, since it is smaller than the sum of its proper divisors (35982700).

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

21418644 is a wasteful number, since it uses less digits than its factorization.

21418644 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 197 (or 195 counting only the distinct ones).

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

The square root of 21418644 is about 4628.0280898024. The cubic root of 21418644 is about 277.7137124906.

The spelling of 21418644 in words is "twenty-one million, four hundred eighteen thousand, six hundred forty-four".