21511102212 has 18 divisors (see below), whose sum is σ = 54375286238. Its totient is φ = 7170367392.

The previous prime is 21511102211. The next prime is 21511102219. The reversal of 21511102212 is 21220111512.

It can be written as a sum of positive squares in only one way, i.e., 20001313476 + 1509788736 = 141426^2 + 38856^2 .

It is a tau number, because it is divible by the number of its divisors (18).

It is a super-2 number, since 2×21511102212² (a number of 21 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is not an unprimeable number, because it can be changed into a prime (21511102211) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 298765273 + ... + 298765344.

Almost surely, 2^21511102212 is an apocalyptic number.

It is an amenable number.

21511102212 is an abundant number, since it is smaller than the sum of its proper divisors (32864184026).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21511102212 is a wasteful number, since it uses less digits than its factorization.

21511102212 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 597530627 (or 597530622 counting only the distinct ones).

The product of its (nonzero) digits is 80, while the sum is 18.

Adding to 21511102212 its reverse (21220111512), we get a palindrome (42731213724).

The spelling of 21511102212 in words is "twenty-one billion, five hundred eleven million, one hundred two thousand, two hundred twelve".