21440220 has 48 divisors (see below), whose sum is σ = 61974528. Its totient is φ = 5532480.

The previous prime is 21440207. The next prime is 21440233. The reversal of 21440220 is 2204412.

It is an interprime number because it is at equal distance from previous prime (21440207) and next prime (21440233).

It is a Harshad number since it is a multiple of its sum of digits (15).

It is a self number, because there is not a number n which added to its sum of digits gives 21440220.

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 15 ways as a sum of consecutive naturals, for example, 3904 + ... + 7623.

It is an arithmetic number, because the mean of its divisors is an integer number (1291136).

Almost surely, 2^21440220 is an apocalyptic number.

21440220 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21440220 is an abundant number, since it is smaller than the sum of its proper divisors (40534308).

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

21440220 is a wasteful number, since it uses less digits than its factorization.

21440220 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11570 (or 11568 counting only the distinct ones).

The product of its (nonzero) digits is 128, while the sum is 15.

The square root of 21440220 is about 4630.3585174369. The cubic root of 21440220 is about 277.8069325251.

Adding to 21440220 its reverse (2204412), we get a palindrome (23644632).

The spelling of 21440220 in words is "twenty-one million, four hundred forty thousand, two hundred twenty".