1221791 has 2 divisors, whose sum is σ = 1221792. Its totient is φ = 1221790.

The previous prime is 1221767. The next prime is 1221793. The reversal of 1221791 is 1971221.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1221791 is a prime.

It is a Sophie Germain prime.

Together with 1221793, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1221793) 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 as a sum of consecutive naturals, namely, 610895 + 610896.

It is an arithmetic number, because the mean of its divisors is an integer number (610896).

2^1221791 is an apocalyptic number.

1221791 is a deficient number, since it is larger than the sum of its proper divisors (1).

1221791 is an equidigital number, since it uses as much as digits as its factorization.

1221791 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 252, while the sum is 23.

The square root of 1221791 is about 1105.3465519917. The cubic root of 1221791 is about 106.9052353382.

The spelling of 1221791 in words is "one million, two hundred twenty-one thousand, seven hundred ninety-one".