21145504 has 48 divisors (see below), whose sum is σ = 43436736. Its totient is φ = 10124800.

The previous prime is 21145489. The next prime is 21145511. The reversal of 21145504 is 40554112.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 93039 + ... + 93265.

It is an arithmetic number, because the mean of its divisors is an integer number (904932).

Almost surely, 2^21145504 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 21145504, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (21718368).

21145504 is an abundant number, since it is smaller than the sum of its proper divisors (22291232).

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

21145504 is a wasteful number, since it uses less digits than its factorization.

21145504 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 349 (or 341 counting only the distinct ones).

The product of its (nonzero) digits is 800, while the sum is 22.

The square root of 21145504 is about 4598.4240778771. The cubic root of 21145504 is about 276.5281492378.

Adding to 21145504 its reverse (40554112), we get a palindrome (61699616).

The spelling of 21145504 in words is "twenty-one million, one hundred forty-five thousand, five hundred four".