21201010991 has 2 divisors, whose sum is σ = 21201010992. Its totient is φ = 21201010990.

The previous prime is 21201010979. The next prime is 21201011003. The reversal of 21201010991 is 19901010212.

It is a balanced prime because it is at equal distance from previous prime (21201010979) and next prime (21201011003).

It is a cyclic number.

It is not a de Polignac number, because 21201010991 - 2⁶ = 21201010927 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21201010991.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21201010591) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10600505495 + 10600505496.

It is an arithmetic number, because the mean of its divisors is an integer number (10600505496).

Almost surely, 2^21201010991 is an apocalyptic number.

21201010991 is a deficient number, since it is larger than the sum of its proper divisors (1).

21201010991 is an equidigital number, since it uses as much as digits as its factorization.

21201010991 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 324, while the sum is 26.

The spelling of 21201010991 in words is "twenty-one billion, two hundred one million, ten thousand, nine hundred ninety-one".