1664351211605 has 4 divisors (see below), whose sum is σ = 1997221453932. Its totient is φ = 1331480969280.

The previous prime is 1664351211577. The next prime is 1664351211661. The reversal of 1664351211605 is 5061121534661.

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 761041630129 + 903309581476 = 872377^2 + 950426^2 .

It is not a de Polignac number, because 1664351211605 - 2¹² = 1664351207509 is a prime.

It is a Duffinian number.

It is a congruent 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 3 ways as a sum of consecutive naturals, for example, 166435121156 + ... + 166435121165.

It is an arithmetic number, because the mean of its divisors is an integer number (499305363483).

Almost surely, 2^{1664351211605} is an apocalyptic number.

It is an amenable number.

1664351211605 is a deficient number, since it is larger than the sum of its proper divisors (332870242327).

1664351211605 is an equidigital number, since it uses as much as digits as its factorization.

1664351211605 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 332870242326.

The product of its (nonzero) digits is 129600, while the sum is 41.

The spelling of 1664351211605 in words is "one trillion, six hundred sixty-four billion, three hundred fifty-one million, two hundred eleven thousand, six hundred five".