21491899319881 has 2 divisors, whose sum is σ = 21491899319882. Its totient is φ = 21491899319880.

The previous prime is 21491899319797. The next prime is 21491899319887. The reversal of 21491899319881 is 18891399819412.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19939841814025 + 1552057505856 = 4465405^2 + 1245816^2 .

It is a cyclic number.

It is not a de Polignac number, because 21491899319881 - 2⁷ = 21491899319753 is a prime.

It is a super-2 number, since 2×21491899319881² (a number of 27 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21491899319887) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10745949659940 + 10745949659941.

It is an arithmetic number, because the mean of its divisors is an integer number (10745949659941).

Almost surely, 2^{21491899319881} is an apocalyptic number.

It is an amenable number.

21491899319881 is a deficient number, since it is larger than the sum of its proper divisors (1).

21491899319881 is an equidigital number, since it uses as much as digits as its factorization.

21491899319881 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 80621568, while the sum is 73.

The spelling of 21491899319881 in words is "twenty-one trillion, four hundred ninety-one billion, eight hundred ninety-nine million, three hundred nineteen thousand, eight hundred eighty-one".