21686424 has 64 divisors (see below), whose sum is σ = 59927040. Its totient is φ = 6504960.

The previous prime is 21686419. The next prime is 21686443. The reversal of 21686424 is 42468612.

It is a nude number because it is divisible by every one of its digits.

It is a congruent number.

It is an unprimeable number.

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 15 ways as a sum of consecutive naturals, for example, 8229 + ... + 10539.

It is an arithmetic number, because the mean of its divisors is an integer number (936360).

Almost surely, 2^21686424 is an apocalyptic number.

21686424 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21686424, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29963520).

21686424 is an abundant number, since it is smaller than the sum of its proper divisors (38240616).

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

21686424 is a wasteful number, since it uses less digits than its factorization.

21686424 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2360 (or 2356 counting only the distinct ones).

The product of its digits is 18432, while the sum is 33.

The square root of 21686424 is about 4656.8684757034. The cubic root of 21686424 is about 278.8662659902.

The spelling of 21686424 in words is "twenty-one million, six hundred eighty-six thousand, four hundred twenty-four".