21220345 has 4 divisors (see below), whose sum is σ = 25464420. Its totient is φ = 16976272.

The previous prime is 21220333. The next prime is 21220349. The reversal of 21220345 is 54302212.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 5822569 + 15397776 = 2413^2 + 3924^2 .

It is a cyclic number.

It is not a de Polignac number, because 21220345 - 2⁵ = 21220313 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21220349) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2122030 + ... + 2122039.

It is an arithmetic number, because the mean of its divisors is an integer number (6366105).

Almost surely, 2^21220345 is an apocalyptic number.

It is an amenable number.

21220345 is a deficient number, since it is larger than the sum of its proper divisors (4244075).

21220345 is an equidigital number, since it uses as much as digits as its factorization.

21220345 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4244074.

The product of its (nonzero) digits is 480, while the sum is 19.

The square root of 21220345 is about 4606.5545693067. The cubic root of 21220345 is about 276.8540069213.

Adding to 21220345 its reverse (54302212), we get a palindrome (75522557).

The spelling of 21220345 in words is "twenty-one million, two hundred twenty thousand, three hundred forty-five".