20001221136 has 120 divisors (see below), whose sum is σ = 62514262720. Its totient is φ = 6154206336.

The previous prime is 20001221083. The next prime is 20001221137. The reversal of 20001221136 is 63112210002.

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 (20001221137) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 147316 + ... + 248403.

Almost surely, 2^20001221136 is an apocalyptic number.

20001221136 is a gapful number since it is divisible by the number (26) formed by its first and last digit.

It is an amenable number.

20001221136 is an abundant number, since it is smaller than the sum of its proper divisors (42513041584).

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

20001221136 is a wasteful number, since it uses less digits than its factorization.

20001221136 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 395755 (or 395737 counting only the distinct ones).

The product of its (nonzero) digits is 144, while the sum is 18.

Adding to 20001221136 its reverse (63112210002), we get a palindrome (83113431138).

The spelling of 20001221136 in words is "twenty billion, one million, two hundred twenty-one thousand, one hundred thirty-six".