1221365443 has 4 divisors (see below), whose sum is σ = 1244410128. Its totient is φ = 1198320760.

The previous prime is 1221365437. The next prime is 1221365447. The reversal of 1221365443 is 3445631221.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 3445631221 = 547 ⋅6299143.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1221365443 is a prime.

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1221365447) 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, 11522263 + ... + 11522368.

It is an arithmetic number, because the mean of its divisors is an integer number (311102532).

Almost surely, 2^1221365443 is an apocalyptic number.

1221365443 is a deficient number, since it is larger than the sum of its proper divisors (23044685).

1221365443 is an equidigital number, since it uses as much as digits as its factorization.

1221365443 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 23044684.

The product of its digits is 17280, while the sum is 31.

The square root of 1221365443 is about 34948.0391867698. The cubic root of 1221365443 is about 1068.9282198922.

Adding to 1221365443 its reverse (3445631221), we get a palindrome (4666996664).

The spelling of 1221365443 in words is "one billion, two hundred twenty-one million, three hundred sixty-five thousand, four hundred forty-three".