21381204 has 48 divisors (see below), whose sum is σ = 54111680. Its totient is φ = 6570720.

The previous prime is 21381203. The next prime is 21381209. The reversal of 21381204 is 40218312.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21381203) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 25959 + ... + 26769.

Almost surely, 2^21381204 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 21381204, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27055840).

21381204 is an abundant number, since it is smaller than the sum of its proper divisors (32730476).

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

21381204 is a wasteful number, since it uses less digits than its factorization.

21381204 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 857 (or 829 counting only the distinct ones).

The product of its (nonzero) digits is 384, while the sum is 21.

The square root of 21381204 is about 4623.9814013467. The cubic root of 21381204 is about 277.5518026820.

Adding to 21381204 its reverse (40218312), we get a palindrome (61599516).

The spelling of 21381204 in words is "twenty-one million, three hundred eighty-one thousand, two hundred four".