1216391 has 4 divisors (see below), whose sum is σ = 1326984. Its totient is φ = 1105800.

The previous prime is 1216387. The next prime is 1216393. The reversal of 1216391 is 1936121.

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 1216391 - 2² = 1216387 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 (1216393) 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, 55280 + ... + 55301.

It is an arithmetic number, because the mean of its divisors is an integer number (331746).

2^1216391 is an apocalyptic number.

1216391 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

1216391 is a deficient number, since it is larger than the sum of its proper divisors (110593).

1216391 is a wasteful number, since it uses less digits than its factorization.

1216391 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 110592.

The product of its digits is 324, while the sum is 23.

The square root of 1216391 is about 1102.9011741765. The cubic root of 1216391 is about 106.7475049098.

The spelling of 1216391 in words is "one million, two hundred sixteen thousand, three hundred ninety-one".