21001108993 has 2 divisors, whose sum is σ = 21001108994. Its totient is φ = 21001108992.

The previous prime is 21001108981. The next prime is 21001109021. The reversal of 21001108993 is 39980110012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 15369056784 + 5632052209 = 123972^2 + 75047^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21001108993 is a prime.

It is not a weakly prime, because it can be changed into another prime (21001108913) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10500554496 + 10500554497.

It is an arithmetic number, because the mean of its divisors is an integer number (10500554497).

Almost surely, 2^21001108993 is an apocalyptic number.

It is an amenable number.

21001108993 is a deficient number, since it is larger than the sum of its proper divisors (1).

21001108993 is an equidigital number, since it uses as much as digits as its factorization.

21001108993 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 3888, while the sum is 34.

The spelling of 21001108993 in words is "twenty-one billion, one million, one hundred eight thousand, nine hundred ninety-three".