21002021120 has 72 divisors (see below), whose sum is σ = 50355628344. Its totient is φ = 8392589312.

The previous prime is 21002021113. The next prime is 21002021123. The reversal of 21002021120 is 2112020012.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 136796416 + 20865224704 = 11696^2 + 144448^2 .

It is a super-2 number, since 2×21002021120² (a number of 21 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21002021123) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1396682 + ... + 1411638.

It is an arithmetic number, because the mean of its divisors is an integer number (699383727).

Almost surely, 2^21002021120 is an apocalyptic number.

21002021120 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 21002021120, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25177814172).

21002021120 is an abundant number, since it is smaller than the sum of its proper divisors (29353607224).

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

21002021120 is a wasteful number, since it uses less digits than its factorization.

21002021120 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16075 (or 16061 counting only the distinct ones).

The product of its (nonzero) digits is 16, while the sum is 11.

Adding to 21002021120 its reverse (2112020012), we get a palindrome (23114041132).

The spelling of 21002021120 in words is "twenty-one billion, two million, twenty-one thousand, one hundred twenty".