21011155511 has 16 divisors (see below), whose sum is σ = 21361747680. Its totient is φ = 20663470080.

The previous prime is 21011155483. The next prime is 21011155549. The reversal of 21011155511 is 11555111012.

It is a cyclic number.

It is not a de Polignac number, because 21011155511 - 2²² = 21006961207 is a prime.

It is a super-2 number, since 2×21011155511² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21011155811) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 19258076 + ... + 19259166.

It is an arithmetic number, because the mean of its divisors is an integer number (1335109230).

Almost surely, 2^21011155511 is an apocalyptic number.

21011155511 is a deficient number, since it is larger than the sum of its proper divisors (350592169).

21011155511 is a wasteful number, since it uses less digits than its factorization.

21011155511 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2146.

The product of its (nonzero) digits is 250, while the sum is 23.

Adding to 21011155511 its reverse (11555111012), we get a palindrome (32566266523).

The spelling of 21011155511 in words is "twenty-one billion, eleven million, one hundred fifty-five thousand, five hundred eleven".