21121000000 has 98 divisors (see below), whose sum is σ = 52391790314. Its totient is φ = 8448000000.

The previous prime is 21120999979. The next prime is 21121000007. The reversal of 21121000000 is 12112.

It can be written as a sum of positive squares in 7 ways, for example, as 20957773824 + 163226176 = 144768^2 + 12776^2 .

It is not an unprimeable number, because it can be changed into a prime (21121000007) by changing a digit.

It is a polite number, since it can be written in 13 ways as a sum of consecutive naturals, for example, 989440 + ... + 1010560.

Almost surely, 2^21121000000 is an apocalyptic number.

21121000000 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21121000000, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26195895157).

21121000000 is an abundant number, since it is smaller than the sum of its proper divisors (31270790314).

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

21121000000 is an frugal number, since it uses more digits than its factorization.

21121000000 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21163 (or 21128 counting only the distinct ones).

The product of its (nonzero) digits is 4, while the sum is 7.

Adding to 21121000000 its reverse (12112), we get a palindrome (21121012112).

The spelling of 21121000000 in words is "twenty-one billion, one hundred twenty-one million", and thus it is an aban number.