21121126660 has 24 divisors (see below), whose sum is σ = 44480030616. Its totient is φ = 8424514560.

The previous prime is 21121126603. The next prime is 21121126679. The reversal of 21121126660 is 6662112112.

It can be written as a sum of positive squares in 4 ways, for example, as 4886289604 + 16234837056 = 69902^2 + 127416^2 .

It is a super-2 number, since 2×21121126660² (a number of 21 digits) contains 22 as substring.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1488771 + ... + 1502890.

It is an arithmetic number, because the mean of its divisors is an integer number (1853334609).

Almost surely, 2^21121126660 is an apocalyptic number.

21121126660 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21121126660 is an abundant number, since it is smaller than the sum of its proper divisors (23358903956).

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

21121126660 is a wasteful number, since it uses less digits than its factorization.

21121126660 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2992023 (or 2992021 counting only the distinct ones).

The product of its (nonzero) digits is 1728, while the sum is 28.

Adding to 21121126660 its reverse (6662112112), we get a palindrome (27783238772).

The spelling of 21121126660 in words is "twenty-one billion, one hundred twenty-one million, one hundred twenty-six thousand, six hundred sixty".