21223145 has 4 divisors (see below), whose sum is σ = 25467780. Its totient is φ = 16978512.

The previous prime is 21223141. The next prime is 21223159. The reversal of 21223145 is 54132212.

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 13366336 + 7856809 = 3656^2 + 2803^2 .

It is a cyclic number.

It is not a de Polignac number, because 21223145 - 2² = 21223141 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21223141) 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, 2122310 + ... + 2122319.

It is an arithmetic number, because the mean of its divisors is an integer number (6366945).

Almost surely, 2^21223145 is an apocalyptic number.

It is an amenable number.

21223145 is a deficient number, since it is larger than the sum of its proper divisors (4244635).

21223145 is an equidigital number, since it uses as much as digits as its factorization.

21223145 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4244634.

The product of its digits is 480, while the sum is 20.

The square root of 21223145 is about 4606.8584740580. The cubic root of 21223145 is about 276.8661832412.

Adding to 21223145 its reverse (54132212), we get a palindrome (75355357).

The spelling of 21223145 in words is "twenty-one million, two hundred twenty-three thousand, one hundred forty-five".