21000121210 has 8 divisors (see below), whose sum is σ = 37800218196. Its totient is φ = 8400048480.

The previous prime is 21000121187. The next prime is 21000121211. The reversal of 21000121210 is 1212100012.

It can be written as a sum of positive squares in 2 ways, for example, as 20917547641 + 82573569 = 144629^2 + 9087^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a Harshad number since it is a multiple of its sum of digits (10), and also a Moran number because the ratio is a prime number: 2100012121 = 21000121210 / (2 + 1 + 0 + 0 + 0 + 1 + 2 + 1 + 2 + 1 + 0).

It is not an unprimeable number, because it can be changed into a prime (21000121211) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1050006051 + ... + 1050006070.

Almost surely, 2^21000121210 is an apocalyptic number.

21000121210 is a deficient number, since it is larger than the sum of its proper divisors (16800096986).

21000121210 is a wasteful number, since it uses less digits than its factorization.

21000121210 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2100012128.

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

Adding to 21000121210 its reverse (1212100012), we get a palindrome (22212221222).

The spelling of 21000121210 in words is "twenty-one billion, one hundred twenty-one thousand, two hundred ten".