21220225 has 12 divisors (see below), whose sum is σ = 28337596. Its totient is φ = 15670080.

The previous prime is 21220223. The next prime is 21220231. The reversal of 21220225 is 52202212.

It can be written as a sum of positive squares in 6 ways, for example, as 2062096 + 19158129 = 1436^2 + 4377^2 .

It is not a de Polignac number, because 21220225 - 2¹ = 21220223 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21220199 and 21220208.

It is not an unprimeable number, because it can be changed into a prime (21220223) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 32322 + ... + 32971.

Almost surely, 2^21220225 is an apocalyptic number.

21220225 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21220225 is a deficient number, since it is larger than the sum of its proper divisors (7117371).

21220225 is a wasteful number, since it uses less digits than its factorization.

21220225 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 65316 (or 65311 counting only the distinct ones).

The product of its (nonzero) digits is 160, while the sum is 16.

The square root of 21220225 is about 4606.5415443693. The cubic root of 21220225 is about 276.8534850551.

Adding to 21220225 its reverse (52202212), we get a palindrome (73422437).

The spelling of 21220225 in words is "twenty-one million, two hundred twenty thousand, two hundred twenty-five".