1221505243 has 4 divisors (see below), whose sum is σ = 1396006000. Its totient is φ = 1047004488.

The previous prime is 1221505237. The next prime is 1221505247. The reversal of 1221505243 is 3425051221.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 3425051221 = 439 ⋅7801939.

It is a cyclic number.

It is not a de Polignac number, because 1221505243 - 2¹⁷ = 1221374171 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1221505247) 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, 87250368 + ... + 87250381.

It is an arithmetic number, because the mean of its divisors is an integer number (349001500).

Almost surely, 2^1221505243 is an apocalyptic number.

1221505243 is a deficient number, since it is larger than the sum of its proper divisors (174500757).

1221505243 is an equidigital number, since it uses as much as digits as its factorization.

1221505243 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 174500756.

The product of its (nonzero) digits is 2400, while the sum is 25.

The square root of 1221505243 is about 34950.0392417519. The cubic root of 1221505243 is about 1068.9690022436.

Adding to 1221505243 its reverse (3425051221), we get a palindrome (4646556464).

The spelling of 1221505243 in words is "one billion, two hundred twenty-one million, five hundred five thousand, two hundred forty-three".