21002001220 has 24 divisors (see below), whose sum is σ = 44440881408. Its totient is φ = 8336671200.

The previous prime is 21002001217. The next prime is 21002001221. The reversal of 21002001220 is 2210020012.

It is a Harshad number since it is a multiple of its sum of digits (10).

It is a junction number, because it is equal to n+sod(n) for n = 21002001197 and 21002001206.

It is not an unprimeable number, because it can be changed into a prime (21002001221) 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, 4005396 + ... + 4010635.

It is an arithmetic number, because the mean of its divisors is an integer number (1851703392).

Almost surely, 2^21002001220 is an apocalyptic number.

21002001220 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21002001220 is an abundant number, since it is smaller than the sum of its proper divisors (23438880188).

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

21002001220 is a wasteful number, since it uses less digits than its factorization.

21002001220 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8016171 (or 8016169 counting only the distinct ones).

The product of its (nonzero) digits is 16, while the sum is 10.

Adding to 21002001220 its reverse (2210020012), we get a palindrome (23212021232).

The spelling of 21002001220 in words is "twenty-one billion, two million, one thousand, two hundred twenty".