664505891 has 8 divisors (see below), whose sum is σ = 773764704. Its totient is φ = 558829440.

The previous prime is 664505833. The next prime is 664505917. The reversal of 664505891 is 198505466.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-664505891 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (664505291) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 895190 + ... + 895931.

It is an arithmetic number, because the mean of its divisors is an integer number (96720588).

Almost surely, 2^664505891 is an apocalyptic number.

664505891 is a deficient number, since it is larger than the sum of its proper divisors (109258813).

664505891 is a wasteful number, since it uses less digits than its factorization.

664505891 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1791181.

The product of its (nonzero) digits is 259200, while the sum is 44.

The square root of 664505891 is about 25778.0117736027. The cubic root of 664505891 is about 872.6356375145.

The spelling of 664505891 in words is "six hundred sixty-four million, five hundred five thousand, eight hundred ninety-one".