21155116613 has 4 divisors (see below), whose sum is σ = 21223139808. Its totient is φ = 21087093420.

The previous prime is 21155116601. The next prime is 21155116621. The reversal of 21155116613 is 31661155112.

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 21155116613 - 2¹⁴ = 21155100229 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 21155116613.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21155176613) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 34011131 + ... + 34011752.

It is an arithmetic number, because the mean of its divisors is an integer number (5305784952).

Almost surely, 2^21155116613 is an apocalyptic number.

It is an amenable number.

21155116613 is a deficient number, since it is larger than the sum of its proper divisors (68023195).

21155116613 is an equidigital number, since it uses as much as digits as its factorization.

21155116613 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 68023194.

The product of its digits is 5400, while the sum is 32.

The spelling of 21155116613 in words is "twenty-one billion, one hundred fifty-five million, one hundred sixteen thousand, six hundred thirteen".