21232240 has 20 divisors (see below), whose sum is σ = 49365144. Its totient is φ = 8492864.

The previous prime is 21232229. The next prime is 21232247. The reversal of 21232240 is 4223212.

It is a tau number, because it is divible by the number of its divisors (20).

It is a Harshad number since it is a multiple of its sum of digits (16).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21232247) 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 3 ways as a sum of consecutive naturals, for example, 132622 + ... + 132781.

Almost surely, 2^21232240 is an apocalyptic number.

21232240 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21232240 is an abundant number, since it is smaller than the sum of its proper divisors (28132904).

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

21232240 is a wasteful number, since it uses less digits than its factorization.

21232240 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 265416 (or 265410 counting only the distinct ones).

The product of its (nonzero) digits is 192, while the sum is 16.

The square root of 21232240 is about 4607.8454835205. The cubic root of 21232240 is about 276.9057271498.

Adding to 21232240 its reverse (4223212), we get a palindrome (25455452).

Subtracting from 21232240 its reverse (4223212), we obtain a triangular number (17009028 = T₅₈₃₂).

The spelling of 21232240 in words is "twenty-one million, two hundred thirty-two thousand, two hundred forty".