1215278191 has 2 divisors, whose sum is σ = 1215278192. Its totient is φ = 1215278190.

The previous prime is 1215278159. The next prime is 1215278203. The reversal of 1215278191 is 1918725121.

It is a strong prime.

It is an emirp because it is prime and its reverse (1918725121) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1215278191 - 2⁵ = 1215278159 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 1215278191.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1215278101) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 607639095 + 607639096.

It is an arithmetic number, because the mean of its divisors is an integer number (607639096).

Almost surely, 2^1215278191 is an apocalyptic number.

1215278191 is a deficient number, since it is larger than the sum of its proper divisors (1).

1215278191 is an equidigital number, since it uses as much as digits as its factorization.

1215278191 is an evil number, because the sum of its binary digits is even.

The product of its digits is 10080, while the sum is 37.

The square root of 1215278191 is about 34860.8403656596. The cubic root of 1215278191 is about 1067.1494251079.

The spelling of 1215278191 in words is "one billion, two hundred fifteen million, two hundred seventy-eight thousand, one hundred ninety-one".