21204378 has 24 divisors (see below), whose sum is σ = 49477428. Its totient is φ = 6524352.

The previous prime is 21204349. The next prime is 21204397. The reversal of 21204378 is 87340212.

21204378 = T₁₅₇ + T₁₅₈ + ... + T₅₀₇.

It can be written as a sum of positive squares in 2 ways, for example, as 20493729 + 710649 = 4527^2 + 843^2 .

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 45075 + ... + 45542.

Almost surely, 2^21204378 is an apocalyptic number.

21204378 is an abundant number, since it is smaller than the sum of its proper divisors (28273050).

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

21204378 is a wasteful number, since it uses less digits than its factorization.

21204378 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 90638 (or 90635 counting only the distinct ones).

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

The square root of 21204378 is about 4604.8211691661. The cubic root of 21204378 is about 276.7845509799.

The spelling of 21204378 in words is "twenty-one million, two hundred four thousand, three hundred seventy-eight".