21121310555 has 4 divisors (see below), whose sum is σ = 25345572672. Its totient is φ = 16897048440.

The previous prime is 21121310503. The next prime is 21121310563. The reversal of 21121310555 is 55501312112.

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

It is not a de Polignac number, because 21121310555 - 2⁶ = 21121310491 is a prime.

It is a super-2 number, since 2×21121310555² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is an unprimeable number.

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, 2112131051 + ... + 2112131060.

It is an arithmetic number, because the mean of its divisors is an integer number (6336393168).

Almost surely, 2^21121310555 is an apocalyptic number.

21121310555 is a deficient number, since it is larger than the sum of its proper divisors (4224262117).

21121310555 is an equidigital number, since it uses as much as digits as its factorization.

21121310555 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4224262116.

The product of its (nonzero) digits is 1500, while the sum is 26.

Adding to 21121310555 its reverse (55501312112), we get a palindrome (76622622667).

The spelling of 21121310555 in words is "twenty-one billion, one hundred twenty-one million, three hundred ten thousand, five hundred fifty-five".