21644334 has 80 divisors (see below), whose sum is σ = 52306848. Its totient is φ = 6671808.

The previous prime is 21644321. The next prime is 21644339. The reversal of 21644334 is 43344612.

21644334 is a `hidden beast` number, since 216 + 443 + 3 + 4 = 666.

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

It is a junction number, because it is equal to n+sod(n) for n = 21644298 and 21644307.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21644339) by changing a digit.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 137784 + ... + 137940.

Almost surely, 2^21644334 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21644334, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26153424).

21644334 is an abundant number, since it is smaller than the sum of its proper divisors (30662514).

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

21644334 is a wasteful number, since it uses less digits than its factorization.

21644334 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 231 (or 222 counting only the distinct ones).

The product of its digits is 6912, while the sum is 27.

The square root of 21644334 is about 4652.3471495580. The cubic root of 21644334 is about 278.6857370276.

Adding to 21644334 its reverse (43344612), we get a palindrome (64988946).

The spelling of 21644334 in words is "twenty-one million, six hundred forty-four thousand, three hundred thirty-four".