21101910997 has 2 divisors, whose sum is σ = 21101910998. Its totient is φ = 21101910996.

The previous prime is 21101910979. The next prime is 21101911063. The reversal of 21101910997 is 79901910112.

Together with previous prime (21101910979) it forms an Ormiston pair, because they use the same digits, order apart.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17374930596 + 3726980401 = 131814^2 + 61049^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21101910997 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21101910937) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10550955498 + 10550955499.

It is an arithmetic number, because the mean of its divisors is an integer number (10550955499).

Almost surely, 2^21101910997 is an apocalyptic number.

It is an amenable number.

21101910997 is a deficient number, since it is larger than the sum of its proper divisors (1).

21101910997 is an equidigital number, since it uses as much as digits as its factorization.

21101910997 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 10206, while the sum is 40.

The spelling of 21101910997 in words is "twenty-one billion, one hundred one million, nine hundred ten thousand, nine hundred ninety-seven".