21947391191221 has 4 divisors (see below), whose sum is σ = 21947790282444. Its totient is φ = 21946992100000.

The previous prime is 21947391191197. The next prime is 21947391191317. The reversal of 21947391191221 is 12219119374912.

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

It can be written as a sum of positive squares in 2 ways, for example, as 701615640625 + 21245775550596 = 837625^2 + 4609314^2 .

It is a cyclic number.

It is not a de Polignac number, because 21947391191221 - 2³³ = 21938801256629 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 (21947391191521) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 199463110 + ... + 199573111.

It is an arithmetic number, because the mean of its divisors is an integer number (5486947570611).

Almost surely, 2^{21947391191221} is an apocalyptic number.

It is an amenable number.

21947391191221 is a deficient number, since it is larger than the sum of its proper divisors (399091223).

21947391191221 is an equidigital number, since it uses as much as digits as its factorization.

21947391191221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 399091222.

The product of its digits is 489888, while the sum is 52.

The spelling of 21947391191221 in words is "twenty-one trillion, nine hundred forty-seven billion, three hundred ninety-one million, one hundred ninety-one thousand, two hundred twenty-one".