40991 has 4 divisors (see below), whose sum is σ = 41400. Its totient is φ = 40584.

The previous prime is 40973. The next prime is 40993. The reversal of 40991 is 19904.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 40991 - 2⁶ = 40927 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 (40993) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 65 + ... + 293.

It is an arithmetic number, because the mean of its divisors is an integer number (10350).

2⁴⁰⁹⁹¹ is an apocalyptic number.

40991 is a deficient number, since it is larger than the sum of its proper divisors (409).

40991 is a wasteful number, since it uses less digits than its factorization.

40991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 408.

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

The square root of 40991 is about 202.4623421775. The cubic root of 40991 is about 34.4796491334.

Adding to 40991 its sum of digits (23), we get a palindrome (41014).

The spelling of 40991 in words is "forty thousand, nine hundred ninety-one".