20121221136 has 80 divisors (see below), whose sum is σ = 53353728000. Its totient is φ = 6531237504.

The previous prime is 20121221129. The next prime is 20121221137. The reversal of 20121221136 is 63112212102.

It is not an unprimeable number, because it can be changed into a prime (20121221137) 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, 426535 + ... + 471353.

It is an arithmetic number, because the mean of its divisors is an integer number (666921600).

Almost surely, 2^20121221136 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 20121221136, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26676864000).

20121221136 is an abundant number, since it is smaller than the sum of its proper divisors (33232506864).

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

20121221136 is a wasteful number, since it uses less digits than its factorization.

20121221136 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 45076 (or 45070 counting only the distinct ones).

The product of its (nonzero) digits is 288, while the sum is 21.

Adding to 20121221136 its reverse (63112212102), we get a palindrome (83233433238).

The spelling of 20121221136 in words is "twenty billion, one hundred twenty-one million, two hundred twenty-one thousand, one hundred thirty-six".