1216881791 has 4 divisors (see below), whose sum is σ = 1223187072. Its totient is φ = 1210576512.

The previous prime is 1216881773. The next prime is 1216881821. The reversal of 1216881791 is 1971886121.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 1216881791 - 2⁶ = 1216881727 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1216881751) by changing a digit.

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, 3152351 + ... + 3152736.

It is an arithmetic number, because the mean of its divisors is an integer number (305796768).

Almost surely, 2^1216881791 is an apocalyptic number.

1216881791 is a deficient number, since it is larger than the sum of its proper divisors (6305281).

1216881791 is an equidigital number, since it uses as much as digits as its factorization.

1216881791 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6305280.

The product of its digits is 48384, while the sum is 44.

The square root of 1216881791 is about 34883.8328026036. The cubic root of 1216881791 is about 1067.6185985270.

The spelling of 1216881791 in words is "one billion, two hundred sixteen million, eight hundred eighty-one thousand, seven hundred ninety-one".