4009991 has 2 divisors, whose sum is σ = 4009992. Its totient is φ = 4009990.

The previous prime is 4009939. The next prime is 4010021. The reversal of 4009991 is 1999004.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 4009991 - 2¹⁰ = 4008967 is a prime.

It is a Sophie Germain prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (4009921) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2004995 + 2004996.

It is an arithmetic number, because the mean of its divisors is an integer number (2004996).

Almost surely, 2^4009991 is an apocalyptic number.

4009991 is a deficient number, since it is larger than the sum of its proper divisors (1).

4009991 is an equidigital number, since it uses as much as digits as its factorization.

4009991 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2916, while the sum is 32.

The square root of 4009991 is about 2002.4961922561. The cubic root of 4009991 is about 158.8721596773.

The spelling of 4009991 in words is "four million, nine thousand, nine hundred ninety-one".