4191991 has 2 divisors, whose sum is σ = 4191992. Its totient is φ = 4191990.

The previous prime is 4191983. The next prime is 4192007. The reversal of 4191991 is 1991914.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 4191991 - 2³ = 4191983 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (4191931) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2095995 + 2095996.

It is an arithmetic number, because the mean of its divisors is an integer number (2095996).

Almost surely, 2^4191991 is an apocalyptic number.

4191991 is a deficient number, since it is larger than the sum of its proper divisors (1).

4191991 is an equidigital number, since it uses as much as digits as its factorization.

4191991 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2916, while the sum is 34.

The square root of 4191991 is about 2047.4352248606. The cubic root of 4191991 is about 161.2402441867.

It can be divided in two parts, 41 and 91991, that multiplied together give a triangular number (3771631 = T₂₇₄₆).

The spelling of 4191991 in words is "four million, one hundred ninety-one thousand, nine hundred ninety-one".