12861157721 has 4 divisors (see below), whose sum is σ = 12906603792. Its totient is φ = 12815711652.

The previous prime is 12861157669. The next prime is 12861157723. The reversal of 12861157721 is 12775116821.

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: 12775116821 = 110291 ⋅115831.

It is a cyclic number.

It is not a de Polignac number, because 12861157721 - 2¹⁸ = 12860895577 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (12861157723) 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, 22722611 + ... + 22723176.

It is an arithmetic number, because the mean of its divisors is an integer number (3226650948).

Almost surely, 2^12861157721 is an apocalyptic number.

It is an amenable number.

12861157721 is a deficient number, since it is larger than the sum of its proper divisors (45446071).

12861157721 is an equidigital number, since it uses as much as digits as its factorization.

12861157721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 45446070.

The product of its digits is 47040, while the sum is 41.

The spelling of 12861157721 in words is "twelve billion, eight hundred sixty-one million, one hundred fifty-seven thousand, seven hundred twenty-one".