6541121665 has 16 divisors (see below), whose sum is σ = 8519712768. Its totient is φ = 4792326336.

The previous prime is 6541121633. The next prime is 6541121689. The reversal of 6541121665 is 5661211456.

It is a cyclic number.

It is not a de Polignac number, because 6541121665 - 2⁵ = 6541121633 is a prime.

It is a Duffinian number.

It is an unprimeable number.

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 15 ways as a sum of consecutive naturals, for example, 387937 + ... + 404446.

It is an arithmetic number, because the mean of its divisors is an integer number (532482048).

Almost surely, 2^6541121665 is an apocalyptic number.

6541121665 is a gapful number since it is divisible by the number (65) formed by its first and last digit.

It is an amenable number.

6541121665 is a deficient number, since it is larger than the sum of its proper divisors (1978591103).

6541121665 is a wasteful number, since it uses less digits than its factorization.

6541121665 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 792528.

The product of its digits is 43200, while the sum is 37.

The square root of 6541121665 is about 80877.2011446984. The cubic root of 6541121665 is about 1870.1828741055.

The spelling of 6541121665 in words is "six billion, five hundred forty-one million, one hundred twenty-one thousand, six hundred sixty-five".