1664197254721 has 4 divisors (see below), whose sum is σ = 1664222148292. Its totient is φ = 1664172361152.

The previous prime is 1664197254719. The next prime is 1664197254773. The reversal of 1664197254721 is 1274527914661.

It is a happy number.

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 56436654096 + 1607760600625 = 237564^2 + 1267975^2 .

It is a cyclic number.

It is not a de Polignac number, because 1664197254721 - 2¹ = 1664197254719 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1664197254701) 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, 12346236 + ... + 12480301.

It is an arithmetic number, because the mean of its divisors is an integer number (416055537073).

Almost surely, 2^{1664197254721} is an apocalyptic number.

It is an amenable number.

1664197254721 is a deficient number, since it is larger than the sum of its proper divisors (24893571).

1664197254721 is an equidigital number, since it uses as much as digits as its factorization.

1664197254721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 24893570.

The product of its digits is 5080320, while the sum is 55.

The spelling of 1664197254721 in words is "one trillion, six hundred sixty-four billion, one hundred ninety-seven million, two hundred fifty-four thousand, seven hundred twenty-one".