491990551601 has 4 divisors (see below), whose sum is σ = 491996553972. Its totient is φ = 491984549232.

The previous prime is 491990551589. The next prime is 491990551609. The reversal of 491990551601 is 106155099194.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 37241280400 + 454749271201 = 192980^2 + 674351^2 .

It is a cyclic number.

It is not a de Polignac number, because 491990551601 - 2¹⁰ = 491990550577 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 491990551601.

It is not an unprimeable number, because it can be changed into a prime (491990551609) 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, 2876510 + ... + 3042743.

It is an arithmetic number, because the mean of its divisors is an integer number (122999138493).

Almost surely, 2^491990551601 is an apocalyptic number.

It is an amenable number.

491990551601 is a deficient number, since it is larger than the sum of its proper divisors (6002371).

491990551601 is an equidigital number, since it uses as much as digits as its factorization.

491990551601 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6002370.

The product of its (nonzero) digits is 437400, while the sum is 50.

The spelling of 491990551601 in words is "four hundred ninety-one billion, nine hundred ninety million, five hundred fifty-one thousand, six hundred one".