21000121012 has 24 divisors (see below), whose sum is σ = 41905220616. Its totient is φ = 9122224128.

The previous prime is 21000120971. The next prime is 21000121031. The reversal of 21000121012 is 21012100012.

It can be written as a sum of positive squares in 4 ways, for example, as 597998116 + 20402122896 = 24454^2 + 142836^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 21000121012.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 11877013 + ... + 11878780.

It is an arithmetic number, because the mean of its divisors is an integer number (1746050859).

Almost surely, 2^21000121012 is an apocalyptic number.

It is an amenable number.

21000121012 is a deficient number, since it is larger than the sum of its proper divisors (20905099604).

21000121012 is a wasteful number, since it uses less digits than its factorization.

21000121012 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 23755827 (or 23755825 counting only the distinct ones).

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

Adding to 21000121012 its reverse (21012100012), we get a palindrome (42012221024).

The spelling of 21000121012 in words is "twenty-one billion, one hundred twenty-one thousand, twelve".