21000010121 has 8 divisors (see below), whose sum is σ = 22599819144. Its totient is φ = 19440702720.

The previous prime is 21000010103. The next prime is 21000010133. The reversal of 21000010121 is 12101000012.

It can be written as a sum of positive squares in 4 ways, for example, as 5577102400 + 15422907721 = 74680^2 + 124189^2 .

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21000010121 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21000010099 and 21000010108.

It is not an unprimeable number, because it can be changed into a prime (21000010721) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 10124330 + ... + 10126403.

It is an arithmetic number, because the mean of its divisors is an integer number (2824977393).

Almost surely, 2^21000010121 is an apocalyptic number.

It is an amenable number.

21000010121 is a deficient number, since it is larger than the sum of its proper divisors (1599809023).

21000010121 is a wasteful number, since it uses less digits than its factorization.

21000010121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20250811.

The product of its (nonzero) digits is 4, while the sum is 8.

Adding to 21000010121 its reverse (12101000012), we get a palindrome (33101010133).

The spelling of 21000010121 in words is "twenty-one billion, ten thousand, one hundred twenty-one".