21645104 has 40 divisors (see below), whose sum is σ = 47549040. Its totient is φ = 9462528.

The previous prime is 21645103. The next prime is 21645109. The reversal of 21645104 is 40154612.

It is a self number, because there is not a number n which added to its sum of digits gives 21645104.

It is not an unprimeable number, because it can be changed into a prime (21645101) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1214 + ... + 6690.

It is an arithmetic number, because the mean of its divisors is an integer number (1188726).

Almost surely, 2^21645104 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 21645104, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (23774520).

21645104 is an abundant number, since it is smaller than the sum of its proper divisors (25903936).

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

21645104 is a wasteful number, since it uses less digits than its factorization.

21645104 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5517 (or 5511 counting only the distinct ones).

The product of its (nonzero) digits is 960, while the sum is 23.

The square root of 21645104 is about 4652.4299027497. The cubic root of 21645104 is about 278.6890417489.

Adding to 21645104 its reverse (40154612), we get a palindrome (61799716).

The spelling of 21645104 in words is "twenty-one million, six hundred forty-five thousand, one hundred four".