21440217 has 4 divisors (see below), whose sum is σ = 28586960. Its totient is φ = 14293476.

The previous prime is 21440207. The next prime is 21440233. The reversal of 21440217 is 71204412.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 21440217 - 2¹⁹ = 20915929 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21440193 and 21440202.

It is not an unprimeable number, because it can be changed into a prime (21440207) 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, 3573367 + ... + 3573372.

It is an arithmetic number, because the mean of its divisors is an integer number (7146740).

Almost surely, 2^21440217 is an apocalyptic number.

It is an amenable number.

21440217 is a deficient number, since it is larger than the sum of its proper divisors (7146743).

21440217 is an equidigital number, since it uses as much as digits as its factorization.

21440217 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7146742.

The product of its (nonzero) digits is 448, while the sum is 21.

The square root of 21440217 is about 4630.3581934878. The cubic root of 21440217 is about 277.8069195678.

Adding to 21440217 its reverse (71204412), we get a palindrome (92644629).

The spelling of 21440217 in words is "twenty-one million, four hundred forty thousand, two hundred seventeen".