221521225 has 6 divisors (see below), whose sum is σ = 274686350. Its totient is φ = 177216960.

The previous prime is 221521217. The next prime is 221521241. The reversal of 221521225 is 522125122.

It can be written as a sum of positive squares in 3 ways, for example, as 15397776 + 206123449 = 3924^2 + 14357^2 .

It is not a de Polignac number, because 221521225 - 2³ = 221521217 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 221521196 and 221521205.

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 4430400 + ... + 4430449.

Almost surely, 2^221521225 is an apocalyptic number.

221521225 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

221521225 is a deficient number, since it is larger than the sum of its proper divisors (53165125).

221521225 is an equidigital number, since it uses as much as digits as its factorization.

221521225 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8860859 (or 8860854 counting only the distinct ones).

The product of its digits is 800, while the sum is 22.

The square root of 221521225 is about 14883.5891168763. The cubic root of 221521225 is about 605.0692951614.

Adding to 221521225 its reverse (522125122), we get a palindrome (743646347).

The spelling of 221521225 in words is "two hundred twenty-one million, five hundred twenty-one thousand, two hundred twenty-five".