4011991 has 2 divisors, whose sum is σ = 4011992. Its totient is φ = 4011990.

The previous prime is 4011979. The next prime is 4012013. The reversal of 4011991 is 1991104.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 4011991 - 2⁷ = 4011863 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (4011911) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2005995 + 2005996.

It is an arithmetic number, because the mean of its divisors is an integer number (2005996).

Almost surely, 2^4011991 is an apocalyptic number.

4011991 is a deficient number, since it is larger than the sum of its proper divisors (1).

4011991 is an equidigital number, since it uses as much as digits as its factorization.

4011991 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 324, while the sum is 25.

The square root of 4011991 is about 2002.9955067349. The cubic root of 4011991 is about 158.8985680083.

The spelling of 4011991 in words is "four million, eleven thousand, nine hundred ninety-one".