21210110001220 has 144 divisors (see below), whose sum is σ = 52835730515568. Its totient is φ = 7128767493120.

The previous prime is 21210110001193. The next prime is 21210110001229. The reversal of 21210110001220 is 2210001101212.

It can be written as a sum of positive squares in 8 ways, for example, as 2979959777536 + 18230150223684 = 1726256^2 + 4269678^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 21210110001220.

It is not an unprimeable number, because it can be changed into a prime (21210110001229) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 61168254 + ... + 61514026.

It is an arithmetic number, because the mean of its divisors is an integer number (366914795247).

Almost surely, 2^{21210110001220} is an apocalyptic number.

21210110001220 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 21210110001220, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26417865257784).

21210110001220 is an abundant number, since it is smaller than the sum of its proper divisors (31625620514348).

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

21210110001220 is a wasteful number, since it uses less digits than its factorization.

21210110001220 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 347030 (or 347021 counting only the distinct ones).

The product of its (nonzero) digits is 16, while the sum is 13.

Adding to 21210110001220 its reverse (2210001101212), we get a palindrome (23420111102432).

The spelling of 21210110001220 in words is "twenty-one trillion, two hundred ten billion, one hundred ten million, one thousand, two hundred twenty".