1668647510521 has 8 divisors (see below), whose sum is σ = 1767197614824. Its totient is φ = 1570141224960.

The previous prime is 1668647510507. The next prime is 1668647510539. The reversal of 1668647510521 is 1250157468661.

It can be written as a sum of positive squares in 4 ways, for example, as 270388560121 + 1398258950400 = 519989^2 + 1182480^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 1668647510521 - 2¹⁵ = 1668647477753 is a prime.

It is not an unprimeable number, because it can be changed into a prime (1668647510821) 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 7 ways as a sum of consecutive naturals, for example, 10876260 + ... + 11028613.

It is an arithmetic number, because the mean of its divisors is an integer number (220899701853).

Almost surely, 2^{1668647510521} is an apocalyptic number.

It is an amenable number.

1668647510521 is a deficient number, since it is larger than the sum of its proper divisors (98550104303).

1668647510521 is a wasteful number, since it uses less digits than its factorization.

1668647510521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21909371.

The product of its (nonzero) digits is 2419200, while the sum is 52.

The spelling of 1668647510521 in words is "one trillion, six hundred sixty-eight billion, six hundred forty-seven million, five hundred ten thousand, five hundred twenty-one".