491109921 has 27 divisors (see below), whose sum is σ = 726189139. Its totient is φ = 319827552.

The previous prime is 491109919. The next prime is 491109947. The reversal of 491109921 is 129901194.

The square root of 491109921 is 22161.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in only one way, i.e., 94303521 + 396806400 = 9711^2 + 19920^2 .

It is not a de Polignac number, because 491109921 - 2¹ = 491109919 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (491109121) by changing a digit.

It is a polite number, since it can be written in 26 ways as a sum of consecutive naturals, for example, 5518045 + ... + 5518133.

Almost surely, 2^491109921 is an apocalyptic number.

491109921 is the 22161-st square number.

491109921 is the 11081-st centered octagonal number.

It is an amenable number.

491109921 is a deficient number, since it is larger than the sum of its proper divisors (235079218).

491109921 is an frugal number, since it uses more digits than its factorization.

491109921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 350 (or 175 counting only the distinct ones).

The product of its (nonzero) digits is 5832, while the sum is 36.

The cubic root of 491109921 is about 788.9683275079.

Multiplying 491109921 by its sum of digits (36), we get a square (17679957156 = 132966²).

The spelling of 491109921 in words is "four hundred ninety-one million, one hundred nine thousand, nine hundred twenty-one".