21187228611 has 4 divisors (see below), whose sum is σ = 28249638152. Its totient is φ = 14124819072.

The previous prime is 21187228609. The next prime is 21187228649. The reversal of 21187228611 is 11682278112.

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

It is not a de Polignac number, because 21187228611 - 2¹ = 21187228609 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21187228611.

It is not an unprimeable number, because it can be changed into a prime (21187228651) 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, 3531204766 + ... + 3531204771.

It is an arithmetic number, because the mean of its divisors is an integer number (7062409538).

Almost surely, 2^21187228611 is an apocalyptic number.

21187228611 is a deficient number, since it is larger than the sum of its proper divisors (7062409541).

21187228611 is an equidigital number, since it uses as much as digits as its factorization.

21187228611 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7062409540.

The product of its digits is 21504, while the sum is 39.

The spelling of 21187228611 in words is "twenty-one billion, one hundred eighty-seven million, two hundred twenty-eight thousand, six hundred eleven".