21155112547 has 4 divisors (see below), whose sum is σ = 21222701080. Its totient is φ = 21087524016.

The previous prime is 21155112499. The next prime is 21155112553. The reversal of 21155112547 is 74521155112.

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

It is a cyclic number.

It is not a de Polignac number, because 21155112547 - 2¹⁵ = 21155079779 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21155112577) 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, 33793797 + ... + 33794422.

It is an arithmetic number, because the mean of its divisors is an integer number (5305675270).

Almost surely, 2^21155112547 is an apocalyptic number.

21155112547 is a deficient number, since it is larger than the sum of its proper divisors (67588533).

21155112547 is an equidigital number, since it uses as much as digits as its factorization.

21155112547 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 67588532.

The product of its digits is 14000, while the sum is 34.

Adding to 21155112547 its reverse (74521155112), we get a palindrome (95676267659).

The spelling of 21155112547 in words is "twenty-one billion, one hundred fifty-five million, one hundred twelve thousand, five hundred forty-seven".