1091671981 has 2 divisors, whose sum is σ = 1091671982. Its totient is φ = 1091671980.

The previous prime is 1091671967. The next prime is 1091671991. The reversal of 1091671981 is 1891761901.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1030987881 + 60684100 = 32109^2 + 7790^2 .

It is a cyclic number.

It is not a de Polignac number, because 1091671981 - 2¹¹ = 1091669933 is a prime.

It is a super-2 number, since 2×1091671981² = 2383495428200928722, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1091671901) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 545835990 + 545835991.

It is an arithmetic number, because the mean of its divisors is an integer number (545835991).

Almost surely, 2^1091671981 is an apocalyptic number.

It is an amenable number.

1091671981 is a deficient number, since it is larger than the sum of its proper divisors (1).

1091671981 is an equidigital number, since it uses as much as digits as its factorization.

1091671981 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 27216, while the sum is 43.

The square root of 1091671981 is about 33040.4597576971. The cubic root of 1091671981 is about 1029.6684077294.

The spelling of 1091671981 in words is "one billion, ninety-one million, six hundred seventy-one thousand, nine hundred eighty-one".