21691332732449 has 2 divisors, whose sum is σ = 21691332732450. Its totient is φ = 21691332732448.

The previous prime is 21691332732347. The next prime is 21691332732451. The reversal of 21691332732449 is 94423723319612.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19734313598224 + 1957019134225 = 4442332^2 + 1398935^2 .

It is a cyclic number.

It is not a de Polignac number, because 21691332732449 - 2²⁰ = 21691331683873 is a prime.

Together with 21691332732451, it forms a pair of twin primes.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 21691332732394 and 21691332732403.

It is not a weakly prime, because it can be changed into another prime (21691332732149) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10845666366224 + 10845666366225.

It is an arithmetic number, because the mean of its divisors is an integer number (10845666366225).

Almost surely, 2^{21691332732449} is an apocalyptic number.

It is an amenable number.

21691332732449 is a deficient number, since it is larger than the sum of its proper divisors (1).

21691332732449 is an equidigital number, since it uses as much as digits as its factorization.

21691332732449 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 11757312, while the sum is 56.

The spelling of 21691332732449 in words is "twenty-one trillion, six hundred ninety-one billion, three hundred thirty-two million, seven hundred thirty-two thousand, four hundred forty-nine".