21212009993 has 2 divisors, whose sum is σ = 21212009994. Its totient is φ = 21212009992.

The previous prime is 21212009899. The next prime is 21212010011. The reversal of 21212009993 is 39990021212.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20233071049 + 978938944 = 142243^2 + 31288^2 .

It is a cyclic number.

It is not a de Polignac number, because 21212009993 - 2¹⁰ = 21212008969 is a prime.

It is not a weakly prime, because it can be changed into another prime (21212059993) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10606004996 + 10606004997.

It is an arithmetic number, because the mean of its divisors is an integer number (10606004997).

Almost surely, 2^21212009993 is an apocalyptic number.

It is an amenable number.

21212009993 is a deficient number, since it is larger than the sum of its proper divisors (1).

21212009993 is an equidigital number, since it uses as much as digits as its factorization.

21212009993 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 17496, while the sum is 38.

The spelling of 21212009993 in words is "twenty-one billion, two hundred twelve million, nine thousand, nine hundred ninety-three".