21102211997 has 2 divisors, whose sum is σ = 21102211998. Its totient is φ = 21102211996.

The previous prime is 21102211993. The next prime is 21102212051. The reversal of 21102211997 is 79911220112.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20947930756 + 154281241 = 144734^2 + 12421^2 .

It is a cyclic number.

It is not a de Polignac number, because 21102211997 - 2² = 21102211993 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21102211993) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10551105998 + 10551105999.

It is an arithmetic number, because the mean of its divisors is an integer number (10551105999).

Almost surely, 2^21102211997 is an apocalyptic number.

It is an amenable number.

21102211997 is a deficient number, since it is larger than the sum of its proper divisors (1).

21102211997 is an equidigital number, since it uses as much as digits as its factorization.

21102211997 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 4536, while the sum is 35.

The spelling of 21102211997 in words is "twenty-one billion, one hundred two million, two hundred eleven thousand, nine hundred ninety-seven".