21210020100 has 90 divisors (see below), whose sum is σ = 68754532154. Its totient is φ = 5656003200.

The previous prime is 21210020053. The next prime is 21210020129. The reversal of 21210020100 is 102001212.

It can be written as a sum of positive squares in 3 ways, for example, as 2218975236 + 18991044864 = 47106^2 + 137808^2 .

It is a tau number, because it is divible by the number of its divisors (90).

It is a Harshad number since it is a multiple of its sum of digits (9).

It is an unprimeable number.

It is a polite number, since it can be written in 29 ways as a sum of consecutive naturals, for example, 1301161 + ... + 1317360.

Almost surely, 2^21210020100 is an apocalyptic number.

21210020100 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21210020100 is an abundant number, since it is smaller than the sum of its proper divisors (47544512054).

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

21210020100 is a wasteful number, since it uses less digits than its factorization.

21210020100 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2618547 (or 2618531 counting only the distinct ones).

The product of its (nonzero) digits is 8, while the sum is 9.

Adding to 21210020100 its reverse (102001212), we get a palindrome (21312021312).

The spelling of 21210020100 in words is "twenty-one billion, two hundred ten million, twenty thousand, one hundred".