13521666661 has 4 divisors (see below), whose sum is σ = 13522851232. Its totient is φ = 13520482092.

The previous prime is 13521666659. The next prime is 13521666713. The reversal of 13521666661 is 16666612531.

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, and also an emirpimes, since its reverse is a distinct semiprime: 16666612531 = 22541 ⋅739391.

It is a cyclic number.

It is not a de Polignac number, because 13521666661 - 2¹ = 13521666659 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (13521666061) 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, 574995 + ... + 598048.

It is an arithmetic number, because the mean of its divisors is an integer number (3380712808).

Almost surely, 2^13521666661 is an apocalyptic number.

It is an amenable number.

13521666661 is a deficient number, since it is larger than the sum of its proper divisors (1184571).

13521666661 is a wasteful number, since it uses less digits than its factorization.

13521666661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1184570.

The product of its digits is 233280, while the sum is 43.

The spelling of 13521666661 in words is "thirteen billion, five hundred twenty-one million, six hundred sixty-six thousand, six hundred sixty-one".