1091551 has 2 divisors, whose sum is σ = 1091552. Its totient is φ = 1091550.

The previous prime is 1091549. The next prime is 1091561. The reversal of 1091551 is 1551901.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 1091551 - 2¹ = 1091549 is a prime.

Together with 1091549, it forms a pair of twin primes.

It is an Ulam number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1091521) 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 as a sum of consecutive naturals, namely, 545775 + 545776.

It is an arithmetic number, because the mean of its divisors is an integer number (545776).

2^1091551 is an apocalyptic number.

1091551 is a deficient number, since it is larger than the sum of its proper divisors (1).

1091551 is an equidigital number, since it uses as much as digits as its factorization.

1091551 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 225, while the sum is 22.

The square root of 1091551 is about 1044.7731811259. The cubic root of 1091551 is about 102.9630369772.

The spelling of 1091551 in words is "one million, ninety-one thousand, five hundred fifty-one".