1991266723 has 2 divisors, whose sum is σ = 1991266724. Its totient is φ = 1991266722.

The previous prime is 1991266649. The next prime is 1991266727. The reversal of 1991266723 is 3276621991.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 1991266723 - 2¹⁷ = 1991135651 is a prime.

It is not a weakly prime, because it can be changed into another prime (1991266727) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 995633361 + 995633362.

It is an arithmetic number, because the mean of its divisors is an integer number (995633362).

Almost surely, 2^1991266723 is an apocalyptic number.

1991266723 is a deficient number, since it is larger than the sum of its proper divisors (1).

1991266723 is an equidigital number, since it uses as much as digits as its factorization.

1991266723 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 244944, while the sum is 46.

The square root of 1991266723 is about 44623.6117207023. The cubic root of 1991266723 is about 1258.0845008588.

The spelling of 1991266723 in words is "one billion, nine hundred ninety-one million, two hundred sixty-six thousand, seven hundred twenty-three".