1261216511 has 2 divisors, whose sum is σ = 1261216512. Its totient is φ = 1261216510.

The previous prime is 1261216441. The next prime is 1261216543. The reversal of 1261216511 is 1156121621.

It is a strong prime.

It is an emirp because it is prime and its reverse (1156121621) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1261216511 - 2¹⁸ = 1260954367 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1261216571) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 630608255 + 630608256.

It is an arithmetic number, because the mean of its divisors is an integer number (630608256).

Almost surely, 2^1261216511 is an apocalyptic number.

1261216511 is a deficient number, since it is larger than the sum of its proper divisors (1).

1261216511 is an equidigital number, since it uses as much as digits as its factorization.

1261216511 is an evil number, because the sum of its binary digits is even.

The product of its digits is 720, while the sum is 26.

The square root of 1261216511 is about 35513.6102219980. The cubic root of 1261216511 is about 1080.4297875047.

The spelling of 1261216511 in words is "one billion, two hundred sixty-one million, two hundred sixteen thousand, five hundred eleven".