664242181 has 4 divisors (see below), whose sum is σ = 669312864. Its totient is φ = 659171500.

The previous prime is 664242169. The next prime is 664242193. The reversal of 664242181 is 181242466.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 181242466 = 2 ⋅90621233.

It is an interprime number because it is at equal distance from previous prime (664242169) and next prime (664242193).

It is a cyclic number.

It is not a de Polignac number, because 664242181 - 2²³ = 655853573 is a prime.

It is a super-2 number, since 2×664242181² = 882435350039273522, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (664242101) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2535145 + ... + 2535406.

It is an arithmetic number, because the mean of its divisors is an integer number (167328216).

Almost surely, 2^664242181 is an apocalyptic number.

It is an amenable number.

664242181 is a deficient number, since it is larger than the sum of its proper divisors (5070683).

664242181 is a wasteful number, since it uses less digits than its factorization.

664242181 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5070682.

The product of its digits is 18432, while the sum is 34.

The square root of 664242181 is about 25772.8962478027. The cubic root of 664242181 is about 872.5201867235.

The spelling of 664242181 in words is "six hundred sixty-four million, two hundred forty-two thousand, one hundred eighty-one".