4001891 has 2 divisors, whose sum is σ = 4001892. Its totient is φ = 4001890.

The previous prime is 4001873. The next prime is 4001939. The reversal of 4001891 is 1981004.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 4001891 - 2⁶ = 4001827 is a prime.

It is a Chen prime.

It is equal to p₂₈₃₂₈₀ and since 4001891 and 283280 have the same sum of digits, it is a Honaker prime.

It is not a weakly prime, because it can be changed into another prime (4001831) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2000945 + 2000946.

It is an arithmetic number, because the mean of its divisors is an integer number (2000946).

Almost surely, 2^4001891 is an apocalyptic number.

4001891 is a deficient number, since it is larger than the sum of its proper divisors (1).

4001891 is an equidigital number, since it uses as much as digits as its factorization.

4001891 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 288, while the sum is 23.

The square root of 4001891 is about 2000.4726941401. The cubic root of 4001891 is about 158.7651160509.

Adding to 4001891 its reverse (1981004), we get a palindrome (5982895).

The spelling of 4001891 in words is "four million, one thousand, eight hundred ninety-one".