1668692447521 has 4 divisors (see below), whose sum is σ = 1820391760944. Its totient is φ = 1516993134100.

The previous prime is 1668692447509. The next prime is 1668692447557. The reversal of 1668692447521 is 1257442968661.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 1668692447521 - 2¹³ = 1668692439329 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 1668692447521.

It is not an unprimeable number, because it can be changed into a prime (1668692447221) 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, 75849656695 + ... + 75849656716.

It is an arithmetic number, because the mean of its divisors is an integer number (455097940236).

Almost surely, 2^{1668692447521} is an apocalyptic number.

1668692447521 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

1668692447521 is a deficient number, since it is larger than the sum of its proper divisors (151699313423).

1668692447521 is a wasteful number, since it uses less digits than its factorization.

1668692447521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 151699313422.

The product of its digits is 34836480, while the sum is 61.

The spelling of 1668692447521 in words is "one trillion, six hundred sixty-eight billion, six hundred ninety-two million, four hundred forty-seven thousand, five hundred twenty-one".