21555215611 has 4 divisors (see below), whose sum is σ = 21634755424. Its totient is φ = 21475675800.

The previous prime is 21555215587. The next prime is 21555215653. The reversal of 21555215611 is 11651255512.

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 21555215611 - 2¹⁷ = 21555084539 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21555215711) 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, 39769500 + ... + 39770041.

It is an arithmetic number, because the mean of its divisors is an integer number (5408688856).

Almost surely, 2^21555215611 is an apocalyptic number.

21555215611 is a deficient number, since it is larger than the sum of its proper divisors (79539813).

21555215611 is an equidigital number, since it uses as much as digits as its factorization.

21555215611 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 79539812.

The product of its digits is 15000, while the sum is 34.

The spelling of 21555215611 in words is "twenty-one billion, five hundred fifty-five million, two hundred fifteen thousand, six hundred eleven".