21011212221020 has 192 divisors, whose sum is σ = 53924950969344. Its totient is φ = 6712895139840.

The previous prime is 21011212221017. The next prime is 21011212221023. The reversal of 21011212221020 is 2012221211012.

It is an interprime number because it is at equal distance from previous prime (21011212221017) and next prime (21011212221023).

It is a Harshad number since it is a multiple of its sum of digits (17).

It is a self number, because there is not a number n which added to its sum of digits gives 21011212221020.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21011212221023) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 97679627 + ... + 97894493.

It is an arithmetic number, because the mean of its divisors is an integer number (280859119632).

Almost surely, 2^{21011212221020} is an apocalyptic number.

21011212221020 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 21011212221020, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26962475484672).

21011212221020 is an abundant number, since it is smaller than the sum of its proper divisors (32913738748324).

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

21011212221020 is a wasteful number, since it uses less digits than its factorization.

21011212221020 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 215308 (or 215306 counting only the distinct ones).

The product of its (nonzero) digits is 64, while the sum is 17.

Adding to 21011212221020 its reverse (2012221211012), we get a palindrome (23023433432032).

The spelling of 21011212221020 in words is "twenty-one trillion, eleven billion, two hundred twelve million, two hundred twenty-one thousand, twenty".