491657987 has 4 divisors (see below), whose sum is σ = 499718016. Its totient is φ = 483597960.

The previous prime is 491657977. The next prime is 491657989. The reversal of 491657987 is 789756194.

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

It is a cyclic number.

It is not a de Polignac number, because 491657987 - 2¹⁸ = 491395843 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (491657989) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4029923 + ... + 4030044.

It is an arithmetic number, because the mean of its divisors is an integer number (124929504).

Almost surely, 2^491657987 is an apocalyptic number.

491657987 is a deficient number, since it is larger than the sum of its proper divisors (8060029).

491657987 is an equidigital number, since it uses as much as digits as its factorization.

491657987 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8060028.

The product of its digits is 3810240, while the sum is 56.

The square root of 491657987 is about 22173.3621041104. The cubic root of 491657987 is about 789.2617078320.

The spelling of 491657987 in words is "four hundred ninety-one million, six hundred fifty-seven thousand, nine hundred eighty-seven".