21223240 has 32 divisors (see below), whose sum is σ = 48920760. Its totient is φ = 8281600.

The previous prime is 21223219. The next prime is 21223261. The reversal of 21223240 is 4232212.

It is an interprime number because it is at equal distance from previous prime (21223219) and next prime (21223261).

It can be written as a sum of positive squares in 4 ways, for example, as 14243076 + 6980164 = 3774^2 + 2642^2 .

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 4831 + ... + 8110.

Almost surely, 2^21223240 is an apocalyptic number.

21223240 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21223240 is an abundant number, since it is smaller than the sum of its proper divisors (27697520).

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

21223240 is a wasteful number, since it uses less digits than its factorization.

21223240 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12993 (or 12989 counting only the distinct ones).

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

The square root of 21223240 is about 4606.8687847604. The cubic root of 21223240 is about 276.8665963476.

Adding to 21223240 its reverse (4232212), we get a palindrome (25455452).

The spelling of 21223240 in words is "twenty-one million, two hundred twenty-three thousand, two hundred forty".