21222405 has 24 divisors (see below), whose sum is σ = 38150112. Its totient is φ = 11317968.

The previous prime is 21222401. The next prime is 21222433. The reversal of 21222405 is 50422212.

It is not a de Polignac number, because 21222405 - 2² = 21222401 is a prime.

It is a Curzon number.

It is a zygodrome in base 4.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21222401) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 7519 + ... + 9948.

It is an arithmetic number, because the mean of its divisors is an integer number (1589588).

Almost surely, 2^21222405 is an apocalyptic number.

It is an amenable number.

21222405 is a deficient number, since it is larger than the sum of its proper divisors (16927707).

21222405 is an equidigital number, since it uses as much as digits as its factorization.

21222405 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 17487 (or 17475 counting only the distinct ones).

The product of its (nonzero) digits is 320, while the sum is 18.

The square root of 21222405 is about 4606.7781583228. The cubic root of 21222405 is about 276.8629653179.

Adding to 21222405 its reverse (50422212), we get a palindrome (71644617).

The spelling of 21222405 in words is "twenty-one million, two hundred twenty-two thousand, four hundred five".