21261011656611 has 32 divisors (see below), whose sum is σ = 29732888719872. Its totient is φ = 13488018635520.

The previous prime is 21261011656603. The next prime is 21261011656631. The reversal of 21261011656611 is 11665611016212.

It is not a de Polignac number, because 21261011656611 - 2³ = 21261011656603 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21261011656611.

It is not an unprimeable number, because it can be changed into a prime (21261011656631) by changing a digit.

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 31 ways as a sum of consecutive naturals, for example, 18261501 + ... + 19390833.

It is an arithmetic number, because the mean of its divisors is an integer number (929152772496).

Almost surely, 2^{21261011656611} is an apocalyptic number.

21261011656611 is a deficient number, since it is larger than the sum of its proper divisors (8471877063261).

21261011656611 is a wasteful number, since it uses less digits than its factorization.

21261011656611 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1130763.

The product of its (nonzero) digits is 25920, while the sum is 39.

The spelling of 21261011656611 in words is "twenty-one trillion, two hundred sixty-one billion, eleven million, six hundred fifty-six thousand, six hundred eleven".