1991954171 has 2 divisors, whose sum is σ = 1991954172. Its totient is φ = 1991954170.

The previous prime is 1991954161. The next prime is 1991954227. The reversal of 1991954171 is 1714591991.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1991954171 is a prime.

It is not a weakly prime, because it can be changed into another prime (1991954131) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 995977085 + 995977086.

It is an arithmetic number, because the mean of its divisors is an integer number (995977086).

Almost surely, 2^1991954171 is an apocalyptic number.

1991954171 is a deficient number, since it is larger than the sum of its proper divisors (1).

1991954171 is an equidigital number, since it uses as much as digits as its factorization.

1991954171 is an evil number, because the sum of its binary digits is even.

The product of its digits is 102060, while the sum is 47.

The square root of 1991954171 is about 44631.3137942409. The cubic root of 1991954171 is about 1258.2292610018.

The spelling of 1991954171 in words is "one billion, nine hundred ninety-one million, nine hundred fifty-four thousand, one hundred seventy-one".