21440020 has 48 divisors (see below), whose sum is σ = 52859520. Its totient is φ = 7150464.

The previous prime is 21440017. The next prime is 21440039. The reversal of 21440020 is 2004412.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 3111 + ... + 7249.

It is an arithmetic number, because the mean of its divisors is an integer number (1101240).

Almost surely, 2^21440020 is an apocalyptic number.

21440020 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 21440020, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26429760).

21440020 is an abundant number, since it is smaller than the sum of its proper divisors (31419500).

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

21440020 is a wasteful number, since it uses less digits than its factorization.

21440020 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4192 (or 4190 counting only the distinct ones).

The product of its (nonzero) digits is 64, while the sum is 13.

The square root of 21440020 is about 4630.3369207867. The cubic root of 21440020 is about 277.8060687037.

Adding to 21440020 its reverse (2004412), we get a palindrome (23444432).

The spelling of 21440020 in words is "twenty-one million, four hundred forty thousand, twenty".