491639817 has 16 divisors (see below), whose sum is σ = 660804480. Its totient is φ = 325126272.

The previous prime is 491639783. The next prime is 491639851. The reversal of 491639817 is 718936194.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (491639783) and next prime (491639851).

It is not a de Polignac number, because 491639817 - 2⁷ = 491639689 is a prime.

It is not an unprimeable number, because it can be changed into a prime (491639857) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 404703 + ... + 405915.

It is an arithmetic number, because the mean of its divisors is an integer number (41300280).

Almost surely, 2^491639817 is an apocalyptic number.

It is an amenable number.

491639817 is a deficient number, since it is larger than the sum of its proper divisors (169164663).

491639817 is a wasteful number, since it uses less digits than its factorization.

491639817 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2192.

The product of its digits is 326592, while the sum is 48.

The square root of 491639817 is about 22172.9523744584. The cubic root of 491639817 is about 789.2519849066.

The spelling of 491639817 in words is "four hundred ninety-one million, six hundred thirty-nine thousand, eight hundred seventeen".