11981398641 has 4 divisors (see below), whose sum is σ = 15975198192. Its totient is φ = 7987599092.

The previous prime is 11981398621. The next prime is 11981398643. The reversal of 11981398641 is 14689318911.

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 11981398641 - 2¹¹ = 11981396593 is a prime.

It is not an unprimeable number, because it can be changed into a prime (11981398643) 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, 1996899771 + ... + 1996899776.

It is an arithmetic number, because the mean of its divisors is an integer number (3993799548).

Almost surely, 2^11981398641 is an apocalyptic number.

It is an amenable number.

11981398641 is a deficient number, since it is larger than the sum of its proper divisors (3993799551).

11981398641 is an equidigital number, since it uses as much as digits as its factorization.

11981398641 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3993799550.

The product of its digits is 373248, while the sum is 51.

The spelling of 11981398641 in words is "eleven billion, nine hundred eighty-one million, three hundred ninety-eight thousand, six hundred forty-one".