664814657 has 4 divisors (see below), whose sum is σ = 715954260. Its totient is φ = 613675056.

The previous prime is 664814641. The next prime is 664814663. The reversal of 664814657 is 756418466.

It is a Cunningham number, because it is equal to 25784²+1.

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 98327056 + 566487601 = 9916^2 + 23801^2 .

It is a cyclic number.

It is not a de Polignac number, because 664814657 - 2⁴ = 664814641 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (664819657) 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, 25569782 + ... + 25569807.

It is an arithmetic number, because the mean of its divisors is an integer number (178988565).

Almost surely, 2^664814657 is an apocalyptic number.

It is an amenable number.

664814657 is a deficient number, since it is larger than the sum of its proper divisors (51139603).

664814657 is a wasteful number, since it uses less digits than its factorization.

664814657 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 51139602.

The product of its digits is 967680, while the sum is 47.

The square root of 664814657 is about 25784.0000193919. Note that the first 4 decimals coincide. The cubic root of 664814657 is about 872.7707747633.

The spelling of 664814657 in words is "six hundred sixty-four million, eight hundred fourteen thousand, six hundred fifty-seven".