221220521 has 4 divisors (see below), whose sum is σ = 227199492. Its totient is φ = 215241552.

The previous prime is 221220499. The next prime is 221220523. The reversal of 221220521 is 125022122.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 125022122 = 2 ⋅62511061.

It can be written as a sum of positive squares in 2 ways, for example, as 121440400 + 99780121 = 11020^2 + 9989^2 .

It is a cyclic number.

It is not a de Polignac number, because 221220521 - 2⁶ = 221220457 is a prime.

It is a super-2 number, since 2×221220521² = 97877037823022882, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 221220521.

It is not an unprimeable number, because it can be changed into a prime (221220523) 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, 2989430 + ... + 2989503.

It is an arithmetic number, because the mean of its divisors is an integer number (56799873).

Almost surely, 2^221220521 is an apocalyptic number.

It is an amenable number.

221220521 is a deficient number, since it is larger than the sum of its proper divisors (5978971).

221220521 is an equidigital number, since it uses as much as digits as its factorization.

221220521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5978970.

The product of its (nonzero) digits is 160, while the sum is 17.

The square root of 221220521 is about 14873.4838218892. The cubic root of 221220521 is about 604.7953874018.

Adding to 221220521 its reverse (125022122), we get a palindrome (346242643).

The spelling of 221220521 in words is "two hundred twenty-one million, two hundred twenty thousand, five hundred twenty-one".