221213261 has 2 divisors, whose sum is σ = 221213262. Its totient is φ = 221213260.

The previous prime is 221213233. The next prime is 221213263. The reversal of 221213261 is 162312122.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 197262025 + 23951236 = 14045^2 + 4894^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-221213261 is a prime.

Together with 221213263, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (221213263) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 110606630 + 110606631.

It is an arithmetic number, because the mean of its divisors is an integer number (110606631).

Almost surely, 2^221213261 is an apocalyptic number.

It is an amenable number.

221213261 is a deficient number, since it is larger than the sum of its proper divisors (1).

221213261 is an equidigital number, since it uses as much as digits as its factorization.

221213261 is an evil number, because the sum of its binary digits is even.

The product of its digits is 288, while the sum is 20.

The square root of 221213261 is about 14873.2397613970. The cubic root of 221213261 is about 604.7887712848.

Adding to 221213261 its reverse (162312122), we get a palindrome (383525383).

The spelling of 221213261 in words is "two hundred twenty-one million, two hundred thirteen thousand, two hundred sixty-one".