21187228613 has 4 divisors (see below), whose sum is σ = 21190991520. Its totient is φ = 21183465708.

The previous prime is 21187228609. The next prime is 21187228649. The reversal of 21187228613 is 31682278112.

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 21187228613 - 2² = 21187228609 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 (21187224613) 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, 1872995 + ... + 1884272.

It is an arithmetic number, because the mean of its divisors is an integer number (5297747880).

Almost surely, 2^21187228613 is an apocalyptic number.

It is an amenable number.

21187228613 is a deficient number, since it is larger than the sum of its proper divisors (3762907).

21187228613 is an equidigital number, since it uses as much as digits as its factorization.

21187228613 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3762906.

The product of its digits is 64512, while the sum is 41.

The spelling of 21187228613 in words is "twenty-one billion, one hundred eighty-seven million, two hundred twenty-eight thousand, six hundred thirteen".