21342420 has 96 divisors (see below), whose sum is σ = 72455040. Its totient is φ = 5172480.

The previous prime is 21342407. The next prime is 21342421. The reversal of 21342420 is 2424312.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a junction number, because it is equal to n+sod(n) for n = 21342393 and 21342402.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21342421) by changing a digit.

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 31 ways as a sum of consecutive naturals, for example, 4144 + ... + 7736.

It is an arithmetic number, because the mean of its divisors is an integer number (754740).

Almost surely, 2^21342420 is an apocalyptic number.

21342420 is a gapful number since it is divisible by the number (20) 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 21342420, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (36227520).

21342420 is an abundant number, since it is smaller than the sum of its proper divisors (51112620).

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

21342420 is a wasteful number, since it uses less digits than its factorization.

21342420 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3622 (or 3614 counting only the distinct ones).

The product of its (nonzero) digits is 384, while the sum is 18.

The square root of 21342420 is about 4619.7857093160. The cubic root of 21342420 is about 277.3838812932.

Adding to 21342420 its reverse (2424312), we get a palindrome (23766732).

It can be divided in two parts, 213424 and 20, that added together give a square (213444 = 462²).

The spelling of 21342420 in words is "twenty-one million, three hundred forty-two thousand, four hundred twenty".