491021791 has 4 divisors (see below), whose sum is σ = 528792712. Its totient is φ = 453250872.

The previous prime is 491021753. The next prime is 491021801. The reversal of 491021791 is 197120194.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 197120194 = 2 ⋅98560097.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-491021791 is a prime.

It is a super-2 number, since 2×491021791² = 482204798473695362, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (491025791) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 18885441 + ... + 18885466.

It is an arithmetic number, because the mean of its divisors is an integer number (132198178).

Almost surely, 2^491021791 is an apocalyptic number.

491021791 is a deficient number, since it is larger than the sum of its proper divisors (37770921).

491021791 is a wasteful number, since it uses less digits than its factorization.

491021791 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 37770920.

The product of its (nonzero) digits is 4536, while the sum is 34.

The square root of 491021791 is about 22159.0115077365. The cubic root of 491021791 is about 788.9211310553.

The spelling of 491021791 in words is "four hundred ninety-one million, twenty-one thousand, seven hundred ninety-one".