21684276 has 18 divisors (see below), whose sum is σ = 54813122. Its totient is φ = 7228080.

The previous prime is 21684241. The next prime is 21684287. The reversal of 21684276 is 67248612.

It can be written as a sum of positive squares in only one way, i.e., 16208676 + 5475600 = 4026^2 + 2340^2 .

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

It is a Harshad number since it is a multiple of its sum of digits (36), and also a Moran number because the ratio is a prime number: 602341 = 21684276 / (2 + 1 + 6 + 8 + 4 + 2 + 7 + 6).

It is a self number, because there is not a number n which added to its sum of digits gives 21684276.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 301135 + ... + 301206.

Almost surely, 2^21684276 is an apocalyptic number.

It is an amenable number.

21684276 is an abundant number, since it is smaller than the sum of its proper divisors (33128846).

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

21684276 is a wasteful number, since it uses less digits than its factorization.

21684276 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 602351 (or 602346 counting only the distinct ones).

The product of its digits is 32256, while the sum is 36.

The square root of 21684276 is about 4656.6378429077. The cubic root of 21684276 is about 278.8570586244.

The spelling of 21684276 in words is "twenty-one million, six hundred eighty-four thousand, two hundred seventy-six".