518668921 has 4 divisors (see below), whose sum is σ = 518822244. Its totient is φ = 518515600.

The previous prime is 518668907. The next prime is 518668993. The reversal of 518668921 is 129866815.

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 115261696 + 403407225 = 10736^2 + 20085^2 .

It is a cyclic number.

It is not a de Polignac number, because 518668921 - 2¹¹ = 518666873 is a prime.

It is a super-2 number, since 2×518668921² = 538034899222608482, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (518668121) 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, 71470 + ... + 78391.

It is an arithmetic number, because the mean of its divisors is an integer number (129705561).

Almost surely, 2^518668921 is an apocalyptic number.

It is an amenable number.

518668921 is a deficient number, since it is larger than the sum of its proper divisors (153323).

518668921 is a wasteful number, since it uses less digits than its factorization.

518668921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 153322.

The product of its digits is 207360, while the sum is 46.

The square root of 518668921 is about 22774.3039630194. The cubic root of 518668921 is about 803.4584239396.

The spelling of 518668921 in words is "five hundred eighteen million, six hundred sixty-eight thousand, nine hundred twenty-one".