12621664020661 has 4 divisors (see below), whose sum is σ = 12621674488192. Its totient is φ = 12621653553132.

The previous prime is 12621664020611. The next prime is 12621664020841. The reversal of 12621664020661 is 16602046612621.

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 a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 12621664020661 - 2¹⁵ = 12621663987893 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 (12621664020611) 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, 3148005 + ... + 5929018.

It is an arithmetic number, because the mean of its divisors is an integer number (3155418622048).

Almost surely, 2^{12621664020661} is an apocalyptic number.

It is an amenable number.

12621664020661 is a deficient number, since it is larger than the sum of its proper divisors (10467531).

12621664020661 is an equidigital number, since it uses as much as digits as its factorization.

12621664020661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10467530.

The product of its (nonzero) digits is 248832, while the sum is 43.

The spelling of 12621664020661 in words is "twelve trillion, six hundred twenty-one billion, six hundred sixty-four million, twenty thousand, six hundred sixty-one".