1216401265 has 4 divisors (see below), whose sum is σ = 1459681524. Its totient is φ = 973121008.

The previous prime is 1216401257. The next prime is 1216401287. The reversal of 1216401265 is 5621046121.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 5621046121 = 151 ⋅37225471.

It can be written as a sum of positive squares in 2 ways, for example, as 851705856 + 364695409 = 29184^2 + 19097^2 .

It is a cyclic number.

It is not a de Polignac number, because 1216401265 - 2³ = 1216401257 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 121640122 + ... + 121640131.

It is an arithmetic number, because the mean of its divisors is an integer number (364920381).

Almost surely, 2^1216401265 is an apocalyptic number.

It is an amenable number.

1216401265 is a deficient number, since it is larger than the sum of its proper divisors (243280259).

1216401265 is an equidigital number, since it uses as much as digits as its factorization.

1216401265 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 243280258.

The product of its (nonzero) digits is 2880, while the sum is 28.

The square root of 1216401265 is about 34876.9446052833. The cubic root of 1216401265 is about 1067.4780518608.

Adding to 1216401265 its reverse (5621046121), we get a palindrome (6837447386).

The spelling of 1216401265 in words is "one billion, two hundred sixteen million, four hundred one thousand, two hundred sixty-five".