221212521 has 6 divisors (see below), whose sum is σ = 319529210. Its totient is φ = 147475008.

The previous prime is 221212501. The next prime is 221212531. The reversal of 221212521 is 125212122.

221212521 is a `hidden beast` number, since 22 + 121 + 2 + 521 = 666.

It can be written as a sum of positive squares in only one way, i.e., 159668496 + 61544025 = 12636^2 + 7845^2 .

It is not a de Polignac number, because 221212521 - 2⁵ = 221212489 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 221212494 and 221212503.

It is not an unprimeable number, because it can be changed into a prime (221212501) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 12289576 + ... + 12289593.

Almost surely, 2^221212521 is an apocalyptic number.

It is an amenable number.

221212521 is a deficient number, since it is larger than the sum of its proper divisors (98316689).

221212521 is a wasteful number, since it uses less digits than its factorization.

221212521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 24579175 (or 24579172 counting only the distinct ones).

The product of its digits is 160, while the sum is 18.

The square root of 221212521 is about 14873.2148844828. The cubic root of 221212521 is about 604.7880969066.

Adding to 221212521 its reverse (125212122), we get a palindrome (346424643).

It can be divided in two parts, 22121 and 2521, that added together give a palindrome (24642).

The spelling of 221212521 in words is "two hundred twenty-one million, two hundred twelve thousand, five hundred twenty-one".