21491899319797 has 2 divisors, whose sum is σ = 21491899319798. Its totient is φ = 21491899319796.

The previous prime is 21491899319789. The next prime is 21491899319881. The reversal of 21491899319797 is 79791399819412.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 16930048368996 + 4561850950801 = 4114614^2 + 2135849^2 .

It is a cyclic number.

It is not a de Polignac number, because 21491899319797 - 2³ = 21491899319789 is a prime.

It is a super-2 number, since 2×21491899319797² (a number of 27 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21491899359797) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10745949659898 + 10745949659899.

It is an arithmetic number, because the mean of its divisors is an integer number (10745949659899).

Almost surely, 2^{21491899319797} is an apocalyptic number.

It is an amenable number.

21491899319797 is a deficient number, since it is larger than the sum of its proper divisors (1).

21491899319797 is an equidigital number, since it uses as much as digits as its factorization.

21491899319797 is an evil number, because the sum of its binary digits is even.

The product of its digits is 555532992, while the sum is 79.

The spelling of 21491899319797 in words is "twenty-one trillion, four hundred ninety-one billion, eight hundred ninety-nine million, three hundred nineteen thousand, seven hundred ninety-seven".