1091691521 has 2 divisors, whose sum is σ = 1091691522. Its totient is φ = 1091691520.

The previous prime is 1091691479. The next prime is 1091691529. The reversal of 1091691521 is 1251961901.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 688485121 + 403206400 = 26239^2 + 20080^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1091691521 is a prime.

It is not a weakly prime, because it can be changed into another prime (1091691529) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 545845760 + 545845761.

It is an arithmetic number, because the mean of its divisors is an integer number (545845761).

Almost surely, 2^1091691521 is an apocalyptic number.

It is an amenable number.

1091691521 is a deficient number, since it is larger than the sum of its proper divisors (1).

1091691521 is an equidigital number, since it uses as much as digits as its factorization.

1091691521 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 4860, while the sum is 35.

The square root of 1091691521 is about 33040.7554544384. The cubic root of 1091691521 is about 1029.6745510890.

The spelling of 1091691521 in words is "one billion, ninety-one million, six hundred ninety-one thousand, five hundred twenty-one".