21378204 has 18 divisors (see below), whose sum is σ = 54039440. Its totient is φ = 7126056.

The previous prime is 21378187. The next prime is 21378209. The reversal of 21378204 is 40287312.

It is a tau number, because it is divible by the number of its divisors (18).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21378209) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 296884 + ... + 296955.

Almost surely, 2^21378204 is an apocalyptic number.

It is an amenable number.

21378204 is an abundant number, since it is smaller than the sum of its proper divisors (32661236).

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

21378204 is a wasteful number, since it uses less digits than its factorization.

21378204 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 593849 (or 593844 counting only the distinct ones).

The product of its (nonzero) digits is 2688, while the sum is 27.

The square root of 21378204 is about 4623.6569941984. The cubic root of 21378204 is about 277.5388209628.

It can be divided in two parts, 21 and 378204, that added together give a square (378225 = 615²).

The spelling of 21378204 in words is "twenty-one million, three hundred seventy-eight thousand, two hundred four".