4000991 has 4 divisors (see below), whose sum is σ = 4036512. Its totient is φ = 3965472.

The previous prime is 4000987. The next prime is 4000993. The reversal of 4000991 is 1990004.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 4000991 - 2² = 4000987 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (4000993) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 17591 + ... + 17816.

It is an arithmetic number, because the mean of its divisors is an integer number (1009128).

Almost surely, 2^4000991 is an apocalyptic number.

4000991 is a deficient number, since it is larger than the sum of its proper divisors (35521).

4000991 is a wasteful number, since it uses less digits than its factorization.

4000991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 35520.

The product of its (nonzero) digits is 324, while the sum is 23.

The square root of 4000991 is about 2000.2477346569. The cubic root of 4000991 is about 158.7532134014.

Adding to 4000991 its reverse (1990004), we get a palindrome (5990995).

The spelling of 4000991 in words is "four million, nine hundred ninety-one", and thus it is an aban number.