21002120224 has 12 divisors (see below), whose sum is σ = 41347924254. Its totient is φ = 10501060096.

The previous prime is 21002120213. The next prime is 21002120257. The reversal of 21002120224 is 42202120012.

It can be written as a sum of positive squares in only one way, i.e., 18468810000 + 2533310224 = 135900^2 + 50332^2 .

It is a Harshad number since it is a multiple of its sum of digits (16).

It is a junction number, because it is equal to n+sod(n) for n = 21002120198 and 21002120207.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 328158097 + ... + 328158160.

Almost surely, 2^21002120224 is an apocalyptic number.

It is an amenable number.

21002120224 is a deficient number, since it is larger than the sum of its proper divisors (20345804030).

21002120224 is an equidigital number, since it uses as much as digits as its factorization.

21002120224 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 656316267 (or 656316259 counting only the distinct ones).

The product of its (nonzero) digits is 128, while the sum is 16.

Adding to 21002120224 its reverse (42202120012), we get a palindrome (63204240236).

The spelling of 21002120224 in words is "twenty-one billion, two million, one hundred twenty thousand, two hundred twenty-four".