1991396923 has 2 divisors, whose sum is σ = 1991396924. Its totient is φ = 1991396922.

The previous prime is 1991396899. The next prime is 1991396929. The reversal of 1991396923 is 3296931991.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 1991396923 - 2⁹ = 1991396411 is a prime.

It is not a weakly prime, because it can be changed into another prime (1991396929) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 995698461 + 995698462.

It is an arithmetic number, because the mean of its divisors is an integer number (995698462).

Almost surely, 2^1991396923 is an apocalyptic number.

1991396923 is a deficient number, since it is larger than the sum of its proper divisors (1).

1991396923 is an equidigital number, since it uses as much as digits as its factorization.

1991396923 is an evil number, because the sum of its binary digits is even.

The product of its digits is 708588, while the sum is 52.

The square root of 1991396923 is about 44625.0705657705. The cubic root of 1991396923 is about 1258.1119204289. Note that the first 3 decimals are identical.

The spelling of 1991396923 in words is "one billion, nine hundred ninety-one million, three hundred ninety-six thousand, nine hundred twenty-three".