21011110009991 has 2 divisors, whose sum is σ = 21011110009992. Its totient is φ = 21011110009990.

The previous prime is 21011110009987. The next prime is 21011110010003. The reversal of 21011110009991 is 19990001111012.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21011110009991 - 2² = 21011110009987 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21011110009951) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10505555004995 + 10505555004996.

It is an arithmetic number, because the mean of its divisors is an integer number (10505555004996).

Almost surely, 2^{21011110009991} is an apocalyptic number.

21011110009991 is a deficient number, since it is larger than the sum of its proper divisors (1).

21011110009991 is an equidigital number, since it uses as much as digits as its factorization.

21011110009991 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1458, while the sum is 35.

The spelling of 21011110009991 in words is "twenty-one trillion, eleven billion, one hundred ten million, nine thousand, nine hundred ninety-one".