21101211997 has 2 divisors, whose sum is σ = 21101211998. Its totient is φ = 21101211996.

The previous prime is 21101211983. The next prime is 21101212031. The reversal of 21101211997 is 79911210112.

It is an a-pointer prime, because the next prime (21101212031) can be obtained adding 21101211997 to its sum of digits (34).

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 11098411801 + 10002800196 = 105349^2 + 100014^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21101211997 is a prime.

It is a super-2 number, since 2×21101211997² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21101211917) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10550605998 + 10550605999.

It is an arithmetic number, because the mean of its divisors is an integer number (10550605999).

Almost surely, 2^21101211997 is an apocalyptic number.

It is an amenable number.

21101211997 is a deficient number, since it is larger than the sum of its proper divisors (1).

21101211997 is an equidigital number, since it uses as much as digits as its factorization.

21101211997 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2268, while the sum is 34.

The spelling of 21101211997 in words is "twenty-one billion, one hundred one million, two hundred eleven thousand, nine hundred ninety-seven".