21004544 has 36 divisors (see below), whose sum is σ = 45744720. Its totient is φ = 9546240.

The previous prime is 21004541. The next prime is 21004547. The reversal of 21004544 is 44540012.

It is an interprime number because it is at equal distance from previous prime (21004541) and next prime (21004547).

It is not an unprimeable number, because it can be changed into a prime (21004541) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 914 + ... + 6545.

Almost surely, 2^21004544 is an apocalyptic number.

It is an amenable number.

21004544 is an abundant number, since it is smaller than the sum of its proper divisors (24740176).

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

21004544 is an equidigital number, since it uses as much as digits as its factorization.

21004544 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7486 (or 7472 counting only the distinct ones).

The product of its (nonzero) digits is 640, while the sum is 20.

The square root of 21004544 is about 4583.0714591854. The cubic root of 21004544 is about 275.9123154910.

Adding to 21004544 its reverse (44540012), we get a palindrome (65544556).

The spelling of 21004544 in words is "twenty-one million, four thousand, five hundred forty-four".