15660621339991 has 4 divisors (see below), whose sum is σ = 15669721063584. Its totient is φ = 15651521616400.

The previous prime is 15660621339971. The next prime is 15660621340003. The reversal of 15660621339991 is 19993312606651.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 15660621339991 - 2⁵ = 15660621339959 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 (15660621339971) 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, 4549859215 + ... + 4549862656.

It is an arithmetic number, because the mean of its divisors is an integer number (3917430265896).

Almost surely, 2^{15660621339991} is an apocalyptic number.

15660621339991 is a deficient number, since it is larger than the sum of its proper divisors (9099723593).

15660621339991 is an equidigital number, since it uses as much as digits as its factorization.

15660621339991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9099723592.

The product of its (nonzero) digits is 14171760, while the sum is 61.

The spelling of 15660621339991 in words is "fifteen trillion, six hundred sixty billion, six hundred twenty-one million, three hundred thirty-nine thousand, nine hundred ninety-one".