21744220 has 24 divisors (see below), whose sum is σ = 45864000. Its totient is φ = 8659392.

The previous prime is 21744209. The next prime is 21744253. The reversal of 21744220 is 2244712.

It is a happy number.

It is a super-2 number, since 2×21744220² = 945622206816800, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21744191 and 21744200.

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, 2506 + ... + 7054.

It is an arithmetic number, because the mean of its divisors is an integer number (1911000).

Almost surely, 2^21744220 is an apocalyptic number.

21744220 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21744220 is an abundant number, since it is smaller than the sum of its proper divisors (24119780).

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

21744220 is a wasteful number, since it uses less digits than its factorization.

21744220 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4797 (or 4795 counting only the distinct ones).

The product of its (nonzero) digits is 896, while the sum is 22.

The square root of 21744220 is about 4663.0698043242. The cubic root of 21744220 is about 279.1137796401.

Adding to 21744220 its reverse (2244712), we get a palindrome (23988932).

The spelling of 21744220 in words is "twenty-one million, seven hundred forty-four thousand, two hundred twenty".