1216588781 has 2 divisors, whose sum is σ = 1216588782. Its totient is φ = 1216588780.

The previous prime is 1216588759. The next prime is 1216588783. The reversal of 1216588781 is 1878856121.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 777015625 + 439573156 = 27875^2 + 20966^2 .

It is a cyclic number.

It is not a de Polignac number, because 1216588781 - 2¹⁴ = 1216572397 is a prime.

It is a super-2 number, since 2×1216588781² = 2960176524110131922, which contains 22 as substring.

Together with 1216588783, 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 (1216588783) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 608294390 + 608294391.

It is an arithmetic number, because the mean of its divisors is an integer number (608294391).

Almost surely, 2^1216588781 is an apocalyptic number.

It is an amenable number.

1216588781 is a deficient number, since it is larger than the sum of its proper divisors (1).

1216588781 is an equidigital number, since it uses as much as digits as its factorization.

1216588781 is an evil number, because the sum of its binary digits is even.

The product of its digits is 215040, while the sum is 47.

The square root of 1216588781 is about 34879.6327532272. The cubic root of 1216588781 is about 1067.5329018885.

The spelling of 1216588781 in words is "one billion, two hundred sixteen million, five hundred eighty-eight thousand, seven hundred eighty-one".