21000010100021 has 2 divisors, whose sum is σ = 21000010100022. Its totient is φ = 21000010100020.

The previous prime is 21000010099973. The next prime is 21000010100029. The reversal of 21000010100021 is 12000101000012.

It is an a-pointer prime, because the next prime (21000010100029) can be obtained adding 21000010100021 to its sum of digits (8).

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 16107459828100 + 4892550271921 = 4013410^2 + 2211911^2 .

It is a cyclic number.

It is not a de Polignac number, because 21000010100021 - 2¹⁰ = 21000010098997 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21000010099981 and 21000010100008.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21000010100029) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10500005050010 + 10500005050011.

It is an arithmetic number, because the mean of its divisors is an integer number (10500005050011).

Almost surely, 2^{21000010100021} is an apocalyptic number.

It is an amenable number.

21000010100021 is a deficient number, since it is larger than the sum of its proper divisors (1).

21000010100021 is an equidigital number, since it uses as much as digits as its factorization.

21000010100021 is an odious number, because the sum of its binary digits is odd.

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

Adding to 21000010100021 its reverse (12000101000012), we get a palindrome (33000111100033).

The spelling of 21000010100021 in words is "twenty-one trillion, ten million, one hundred thousand, twenty-one".