21020304 has 20 divisors (see below), whose sum is σ = 54302576. Its totient is φ = 7006752.

The previous prime is 21020303. The next prime is 21020339. The reversal of 21020304 is 40302012.

It is a Harshad number since it is a multiple of its sum of digits (12).

It is a self number, because there is not a number n which added to its sum of digits gives 21020304.

It is not an unprimeable number, because it can be changed into a prime (21020303) 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, 218914 + ... + 219009.

Almost surely, 2^21020304 is an apocalyptic number.

21020304 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

21020304 is an abundant number, since it is smaller than the sum of its proper divisors (33282272).

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

21020304 is a wasteful number, since it uses less digits than its factorization.

21020304 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 437934 (or 437928 counting only the distinct ones).

The product of its (nonzero) digits is 48, while the sum is 12.

The square root of 21020304 is about 4584.7905077550. The cubic root of 21020304 is about 275.9813051820.

Adding to 21020304 its reverse (40302012), we get a palindrome (61322316).

It can be divided in two parts, 2 and 1020304, that added together give a triangular number (1020306 = T₁₄₂₈).

The spelling of 21020304 in words is "twenty-one million, twenty thousand, three hundred four".