1216891 has 4 divisors (see below), whose sum is σ = 1310512. Its totient is φ = 1123272.

The previous prime is 1216879. The next prime is 1216903. The reversal of 1216891 is 1986121.

It is a happy number.

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

It is an interprime number because it is at equal distance from previous prime (1216879) and next prime (1216903).

It is a cyclic number.

It is not a de Polignac number, because 1216891 - 2⁷ = 1216763 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1216841) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 46791 + ... + 46816.

It is an arithmetic number, because the mean of its divisors is an integer number (327628).

2^1216891 is an apocalyptic number.

1216891 is a deficient number, since it is larger than the sum of its proper divisors (93621).

1216891 is an equidigital number, since it uses as much as digits as its factorization.

1216891 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 93620.

The product of its digits is 864, while the sum is 28.

The square root of 1216891 is about 1103.1278257754. The cubic root of 1216891 is about 106.7621291660.

The spelling of 1216891 in words is "one million, two hundred sixteen thousand, eight hundred ninety-one".