21021220100 has 18 divisors (see below), whose sum is σ = 45616047834. Its totient is φ = 8408488000.

The previous prime is 21021220081. The next prime is 21021220117. The reversal of 21021220100 is 102212012.

It is a happy number.

It can be written as a sum of positive squares in 3 ways, for example, as 2544798916 + 18476421184 = 50446^2 + 135928^2 .

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 5 ways as a sum of consecutive naturals, for example, 105106001 + ... + 105106200.

Almost surely, 2^21021220100 is an apocalyptic number.

21021220100 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21021220100 is an abundant number, since it is smaller than the sum of its proper divisors (24594827734).

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

21021220100 is a wasteful number, since it uses less digits than its factorization.

21021220100 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 210212215 (or 210212208 counting only the distinct ones).

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

Adding to 21021220100 its reverse (102212012), we get a palindrome (21123432112).

The spelling of 21021220100 in words is "twenty-one billion, twenty-one million, two hundred twenty thousand, one hundred".