20021221920 has 192 divisors, whose sum is σ = 72791260416. Its totient is φ = 4530892800.

The previous prime is 20021221901. The next prime is 20021221921. The reversal of 20021221920 is 2912212002.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (21).

It is not an unprimeable number, because it can be changed into a prime (20021221921) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 309862 + ... + 368858.

It is an arithmetic number, because the mean of its divisors is an integer number (379121148).

Almost surely, 2^20021221920 is an apocalyptic number.

20021221920 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 20021221920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (36395630208).

20021221920 is an abundant number, since it is smaller than the sum of its proper divisors (52770038496).

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

20021221920 is a wasteful number, since it uses less digits than its factorization.

20021221920 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 59123 (or 59115 counting only the distinct ones).

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

Adding to 20021221920 its reverse (2912212002), we get a palindrome (22933433922).

The spelling of 20021221920 in words is "twenty billion, twenty-one million, two hundred twenty-one thousand, nine hundred twenty".