21684124 has 48 divisors (see below), whose sum is σ = 49383936. Its totient is φ = 8078400.

The previous prime is 21684077. The next prime is 21684127. The reversal of 21684124 is 42148612.

It is a Smith number, since the sum of its digits (28) coincides with the sum of the digits of its prime factors.

It is a Harshad number since it is a multiple of its sum of digits (28).

It is a junction number, because it is equal to n+sod(n) for n = 21684092 and 21684101.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21684127) 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, 5554 + ... + 8614.

It is an arithmetic number, because the mean of its divisors is an integer number (1028832).

Almost surely, 2^21684124 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 21684124, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24691968).

21684124 is an abundant number, since it is smaller than the sum of its proper divisors (27699812).

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

21684124 is a wasteful number, since it uses less digits than its factorization.

21684124 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3106 (or 3104 counting only the distinct ones).

The product of its digits is 3072, while the sum is 28.

The square root of 21684124 is about 4656.6215220909. The cubic root of 21684124 is about 278.8564070559.

The spelling of 21684124 in words is "twenty-one million, six hundred eighty-four thousand, one hundred twenty-four".