21261332120 has 128 divisors (see below), whose sum is σ = 57672000000. Its totient is φ = 6891236352.

The previous prime is 21261332119. The next prime is 21261332123. The reversal of 21261332120 is 2123316212.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21261332123) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 2650676 + ... + 2658684.

It is an arithmetic number, because the mean of its divisors is an integer number (450562500).

Almost surely, 2^21261332120 is an apocalyptic number.

21261332120 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 21261332120, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28836000000).

21261332120 is an abundant number, since it is smaller than the sum of its proper divisors (36410667880).

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

21261332120 is a wasteful number, since it uses less digits than its factorization.

21261332120 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8545 (or 8541 counting only the distinct ones).

The product of its (nonzero) digits is 864, while the sum is 23.

Adding to 21261332120 its reverse (2123316212), we get a palindrome (23384648332).

The spelling of 21261332120 in words is "twenty-one billion, two hundred sixty-one million, three hundred thirty-two thousand, one hundred twenty".