21281204 has 12 divisors (see below), whose sum is σ = 42562464. Its totient is φ = 9120504.

The previous prime is 21281203. The next prime is 21281207. The reversal of 21281204 is 40218212.

It is a happy number.

21281204 is an admirable number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21281201) 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, 379994 + ... + 380049.

It is an arithmetic number, because the mean of its divisors is an integer number (3546872).

Almost surely, 2^21281204 is an apocalyptic number.

It is an amenable number.

21281204 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

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

21281204 is a wasteful number, since it uses less digits than its factorization.

21281204 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 760054 (or 760052 counting only the distinct ones).

The product of its (nonzero) digits is 256, while the sum is 20.

The square root of 21281204 is about 4613.1555360729. The cubic root of 21281204 is about 277.1184226063.

Adding to 21281204 its reverse (40218212), we get a palindrome (61499416).

The spelling of 21281204 in words is "twenty-one million, two hundred eighty-one thousand, two hundred four".