42491 has 2 divisors, whose sum is σ = 42492. Its totient is φ = 42490.

The previous prime is 42487. The next prime is 42499. The reversal of 42491 is 19424.

42491 = T₁₁₆ + T₁₁₇ + ... + T₁₂₁.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 42491 - 2² = 42487 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (42499) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 21245 + 21246.

It is an arithmetic number, because the mean of its divisors is an integer number (21246).

2⁴²⁴⁹¹ is an apocalyptic number.

42491 is a deficient number, since it is larger than the sum of its proper divisors (1).

42491 is an equidigital number, since it uses as much as digits as its factorization.

42491 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 288, while the sum is 20.

The square root of 42491 is about 206.1334519189. The cubic root of 42491 is about 34.8951966964.

It can be divided in two parts, 424 and 91, that added together give a palindrome (515).

The spelling of 42491 in words is "forty-two thousand, four hundred ninety-one".