21012100121 has 8 divisors (see below), whose sum is σ = 21057256200. Its totient is φ = 20966993280.

The previous prime is 21012100103. The next prime is 21012100159. The reversal of 21012100121 is 12100121012.

It can be written as a sum of positive squares in 4 ways, for example, as 2288282896 + 18723817225 = 47836^2 + 136835^2 .

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-21012100121 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21012106121) 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, 915575 + ... + 938243.

It is an arithmetic number, because the mean of its divisors is an integer number (2632157025).

Almost surely, 2^21012100121 is an apocalyptic number.

It is an amenable number.

21012100121 is a deficient number, since it is larger than the sum of its proper divisors (45156079).

21012100121 is a wasteful number, since it uses less digits than its factorization.

21012100121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 24619.

The product of its (nonzero) digits is 8, while the sum is 11.

Adding to 21012100121 its reverse (12100121012), we get a palindrome (33112221133).

The spelling of 21012100121 in words is "twenty-one billion, twelve million, one hundred thousand, one hundred twenty-one".