21421024 has 48 divisors (see below), whose sum is σ = 44770320. Its totient is φ = 10071040.

The previous prime is 21420991. The next prime is 21421051. The reversal of 21421024 is 42012412.

It is a Harshad number since it is a multiple of its sum of digits (16).

It is a junction number, because it is equal to n+sod(n) for n = 21420989 and 21421007.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 37767 + ... + 38329.

It is an arithmetic number, because the mean of its divisors is an integer number (932715).

Almost surely, 2^21421024 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 21421024, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (22385160).

21421024 is an abundant number, since it is smaller than the sum of its proper divisors (23349296).

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

21421024 is a wasteful number, since it uses less digits than its factorization.

21421024 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 643 (or 635 counting only the distinct ones).

The product of its (nonzero) digits is 128, while the sum is 16.

The square root of 21421024 is about 4628.2852116092. The cubic root of 21421024 is about 277.7239984539.

Adding to 21421024 its reverse (42012412), we get a palindrome (63433436).

The spelling of 21421024 in words is "twenty-one million, four hundred twenty-one thousand, twenty-four".