21684438 has 24 divisors (see below), whose sum is σ = 48499776. Its totient is φ = 6994800.

The previous prime is 21684413. The next prime is 21684461. The reversal of 21684438 is 83448612.

21684438 is a `hidden beast` number, since 216 + 8 + 4 + 438 = 666.

It is a Curzon number.

It is a congruent number.

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, 18873 + ... + 19988.

It is an arithmetic number, because the mean of its divisors is an integer number (2020824).

Almost surely, 2^21684438 is an apocalyptic number.

21684438 is an abundant number, since it is smaller than the sum of its proper divisors (26815338).

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

21684438 is a wasteful number, since it uses less digits than its factorization.

21684438 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 38900 (or 38897 counting only the distinct ones).

The product of its digits is 36864, while the sum is 36.

The square root of 21684438 is about 4656.6552373995. The cubic root of 21684438 is about 278.8577530558.

It can be divided in two parts, 21684 and 438, that added together give a palindrome (22122).

The spelling of 21684438 in words is "twenty-one million, six hundred eighty-four thousand, four hundred thirty-eight".