668657291 has 4 divisors (see below), whose sum is σ = 703849800. Its totient is φ = 633464784.

The previous prime is 668657251. The next prime is 668657309. The reversal of 668657291 is 192756866.

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 668657291 - 2²² = 664462987 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (668657201) 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, 17596226 + ... + 17596263.

It is an arithmetic number, because the mean of its divisors is an integer number (175962450).

Almost surely, 2^668657291 is an apocalyptic number.

668657291 is a deficient number, since it is larger than the sum of its proper divisors (35192509).

668657291 is a wasteful number, since it uses less digits than its factorization.

668657291 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 35192508.

The product of its digits is 1088640, while the sum is 50.

The square root of 668657291 is about 25858.4085163801. The cubic root of 668657291 is about 874.4490860249.

The spelling of 668657291 in words is "six hundred sixty-eight million, six hundred fifty-seven thousand, two hundred ninety-one".