21011001220 has 48 divisors (see below), whose sum is σ = 48630572928. Its totient is φ = 7561589760.

The previous prime is 21011001217. The next prime is 21011001251. The reversal of 21011001220 is 2210011012.

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 = 21011001197 and 21011001206.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 470952 + ... + 513631.

It is an arithmetic number, because the mean of its divisors is an integer number (1013136936).

Almost surely, 2^21011001220 is an apocalyptic number.

21011001220 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21011001220 is an abundant number, since it is smaller than the sum of its proper divisors (27619571708).

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

21011001220 is a wasteful number, since it uses less digits than its factorization.

21011001220 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 984700 (or 984698 counting only the distinct ones).

The product of its (nonzero) digits is 8, while the sum is 10.

Adding to 21011001220 its reverse (2210011012), we get a palindrome (23221012232).

The spelling of 21011001220 in words is "twenty-one billion, eleven million, one thousand, two hundred twenty".