12891019821 has 4 divisors (see below), whose sum is σ = 17188026432. Its totient is φ = 8594013212.

The previous prime is 12891019781. The next prime is 12891019831.

It is a happy number.

12891019821 is nontrivially palindromic in base 10.

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 12891019821 - 2¹⁷ = 12890888749 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (12891019831) 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, 2148503301 + ... + 2148503306.

It is an arithmetic number, because the mean of its divisors is an integer number (4297006608).

Almost surely, 2^12891019821 is an apocalyptic number.

It is an amenable number.

12891019821 is a deficient number, since it is larger than the sum of its proper divisors (4297006611).

12891019821 is an equidigital number, since it uses as much as digits as its factorization.

12891019821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4297006610.

The product of its (nonzero) digits is 20736, while the sum is 42.

The spelling of 12891019821 in words is "twelve billion, eight hundred ninety-one million, nineteen thousand, eight hundred twenty-one".