40391 has 6 divisors (see below), whose sum is σ = 43920. Its totient is φ = 37128.

The previous prime is 40387. The next prime is 40423. The reversal of 40391 is 19304.

It is not a de Polignac number, because 40391 - 2² = 40387 is a prime.

It is an Ulam number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (40351) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 50 + ... + 288.

It is an arithmetic number, because the mean of its divisors is an integer number (7320).

2⁴⁰³⁹¹ is an apocalyptic number.

40391 is a deficient number, since it is larger than the sum of its proper divisors (3529).

40391 is a wasteful number, since it uses less digits than its factorization.

40391 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 265 (or 252 counting only the distinct ones).

The product of its (nonzero) digits is 108, while the sum is 17.

The square root of 40391 is about 200.9751228386. The cubic root of 40391 is about 34.3105912378.

Adding to 40391 its reverse (19304), we get a palindrome (59695).

It can be divided in two parts, 403 and 91, that added together give a palindrome (494).

The spelling of 40391 in words is "forty thousand, three hundred ninety-one".