21420444 has 24 divisors (see below), whose sum is σ = 51705360. Its totient is φ = 6893824.

The previous prime is 21420439. The next prime is 21420449. The reversal of 21420444 is 44402412.

It is an interprime number because it is at equal distance from previous prime (21420439) and next prime (21420449).

It is a self number, because there is not a number n which added to its sum of digits gives 21420444.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21420449) by changing a digit.

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, 30429 + ... + 31124.

It is an arithmetic number, because the mean of its divisors is an integer number (2154390).

Almost surely, 2^21420444 is an apocalyptic number.

It is an amenable number.

21420444 is an abundant number, since it is smaller than the sum of its proper divisors (30284916).

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

21420444 is a wasteful number, since it uses less digits than its factorization.

21420444 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 61589 (or 61587 counting only the distinct ones).

The product of its (nonzero) digits is 1024, while the sum is 21.

The square root of 21420444 is about 4628.2225529894. Note that the first 3 decimals coincide. The cubic root of 21420444 is about 277.7214918608.

Adding to 21420444 its reverse (44402412), we get a palindrome (65822856).

The spelling of 21420444 in words is "twenty-one million, four hundred twenty thousand, four hundred forty-four".