6665221291 has 4 divisors (see below), whose sum is σ = 6666712552. Its totient is φ = 6663730032.

The previous prime is 6665221259. The next prime is 6665221301. The reversal of 6665221291 is 1921225666.

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 6665221291 - 2⁵ = 6665221259 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (6665291291) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 738906 + ... + 747871.

It is an arithmetic number, because the mean of its divisors is an integer number (1666678138).

Almost surely, 2^6665221291 is an apocalyptic number.

6665221291 is a deficient number, since it is larger than the sum of its proper divisors (1491261).

6665221291 is a wasteful number, since it uses less digits than its factorization.

6665221291 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1491260.

The product of its digits is 77760, while the sum is 40.

The square root of 6665221291 is about 81640.8065308030. The cubic root of 6665221291 is about 1881.9360328735.

The spelling of 6665221291 in words is "six billion, six hundred sixty-five million, two hundred twenty-one thousand, two hundred ninety-one".