21290304 has 168 divisors, whose sum is σ = 68567808. Its totient is φ = 5806080.

The previous prime is 21290303. The next prime is 21290323. The reversal of 21290304 is 40309212.

It is a tau number, because it is divible by the number of its divisors (168).

It is a Harshad number since it is a multiple of its sum of digits (21).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21290303) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 291612 + ... + 291684.

Almost surely, 2^21290304 is an apocalyptic number.

21290304 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21290304, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34283904).

21290304 is an abundant number, since it is smaller than the sum of its proper divisors (47277504).

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

21290304 is a wasteful number, since it uses less digits than its factorization.

21290304 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 133 (or 116 counting only the distinct ones).

The product of its (nonzero) digits is 432, while the sum is 21.

The square root of 21290304 is about 4614.1417403457. The cubic root of 21290304 is about 277.1579162722.

Adding to 21290304 its reverse (40309212), we get a palindrome (61599516).

The spelling of 21290304 in words is "twenty-one million, two hundred ninety thousand, three hundred four".