21001021200 has 120 divisors (see below), whose sum is σ = 74748117600. Its totient is φ = 5600269440.

The previous prime is 21001021187. The next prime is 21001021219. The reversal of 21001021200 is 212010012.

It is a tau number, because it is divible by the number of its divisors (120).

It is a super-3 number, since 3×21001021200³ (a number of 32 digits) contains 333 as substring.

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 23 ways as a sum of consecutive naturals, for example, 961470 + ... + 983069.

It is an arithmetic number, because the mean of its divisors is an integer number (622900980).

Almost surely, 2^21001021200 is an apocalyptic number.

21001021200 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21001021200 is an abundant number, since it is smaller than the sum of its proper divisors (53747096400).

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

21001021200 is a wasteful number, since it uses less digits than its factorization.

21001021200 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1944566 (or 1944549 counting only the distinct ones).

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

Adding to 21001021200 its reverse (212010012), we get a palindrome (21213031212).

The spelling of 21001021200 in words is "twenty-one billion, one million, twenty-one thousand, two hundred".