491020668 has 18 divisors (see below), whose sum is σ = 1241191224. Its totient is φ = 163673544.

The previous prime is 491020661. The next prime is 491020669. The reversal of 491020668 is 866020194.

It is a tau number, because it is divible by the number of its divisors (18).

It is a super-2 number, since 2×491020668² = 482202592806332448, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (36), and also a Moran number because the ratio is a prime number: 13639463 = 491020668 / (4 + 9 + 1 + 0 + 2 + 0 + 6 + 6 + 8).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (491020661) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 6819696 + ... + 6819767.

It is an arithmetic number, because the mean of its divisors is an integer number (68955068).

Almost surely, 2^491020668 is an apocalyptic number.

It is an amenable number.

491020668 is an abundant number, since it is smaller than the sum of its proper divisors (750170556).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

491020668 is a wasteful number, since it uses less digits than its factorization.

491020668 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13639473 (or 13639468 counting only the distinct ones).

The product of its (nonzero) digits is 20736, while the sum is 36.

The square root of 491020668 is about 22158.9861681441. The cubic root of 491020668 is about 788.9205296162.

The spelling of 491020668 in words is "four hundred ninety-one million, twenty thousand, six hundred sixty-eight".