21009998953 has 2 divisors, whose sum is σ = 21009998954. Its totient is φ = 21009998952.

The previous prime is 21009998939. The next prime is 21009998987. The reversal of 21009998953 is 35989990012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 14248719424 + 6761279529 = 119368^2 + 82227^2 .

It is a cyclic number.

It is not a de Polignac number, because 21009998953 - 2²⁹ = 20473128041 is a prime.

It is a super-2 number, since 2×21009998953² (a number of 21 digits) contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21009998894 and 21009998903.

It is not a weakly prime, because it can be changed into another prime (21009998453) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10504999476 + 10504999477.

It is an arithmetic number, because the mean of its divisors is an integer number (10504999477).

Almost surely, 2^21009998953 is an apocalyptic number.

It is an amenable number.

21009998953 is a deficient number, since it is larger than the sum of its proper divisors (1).

21009998953 is an equidigital number, since it uses as much as digits as its factorization.

21009998953 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1574640, while the sum is 55.

The spelling of 21009998953 in words is "twenty-one billion, nine million, nine hundred ninety-eight thousand, nine hundred fifty-three".