21000001220 has 24 divisors (see below), whose sum is σ = 48109094208. Its totient is φ = 7636364000.

The previous prime is 21000001201. The next prime is 21000001249. The reversal of 21000001220 is 2210000012.

It is a junction number, because it is equal to n+sod(n) for n = 21000001198 and 21000001207.

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 7 ways as a sum of consecutive naturals, for example, 47727056 + ... + 47727495.

It is an arithmetic number, because the mean of its divisors is an integer number (2004545592).

Almost surely, 2^21000001220 is an apocalyptic number.

21000001220 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21000001220 is an abundant number, since it is smaller than the sum of its proper divisors (27109092988).

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

21000001220 is a wasteful number, since it uses less digits than its factorization.

21000001220 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 95454571 (or 95454569 counting only the distinct ones).

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

Adding to 21000001220 its reverse (2210000012), we get a palindrome (23210001232).

The spelling of 21000001220 in words is "twenty-one billion, one thousand, two hundred twenty".