243531221 has 2 divisors, whose sum is σ = 243531222. Its totient is φ = 243531220.

The previous prime is 243531217. The next prime is 243531229. The reversal of 243531221 is 122135342.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 236698225 + 6832996 = 15385^2 + 2614^2 .

It is a cyclic number.

It is not a de Polignac number, because 243531221 - 2² = 243531217 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (243531229) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 121765610 + 121765611.

It is an arithmetic number, because the mean of its divisors is an integer number (121765611).

Almost surely, 2^243531221 is an apocalyptic number.

It is an amenable number.

243531221 is a deficient number, since it is larger than the sum of its proper divisors (1).

243531221 is an equidigital number, since it uses as much as digits as its factorization.

243531221 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1440, while the sum is 23.

The square root of 243531221 is about 15605.4868876303. The cubic root of 243531221 is about 624.4795419711.

Adding to 243531221 its reverse (122135342), we get a palindrome (365666563).

The spelling of 243531221 in words is "two hundred forty-three million, five hundred thirty-one thousand, two hundred twenty-one".