21391733749 has 2 divisors, whose sum is σ = 21391733750. Its totient is φ = 21391733748.

The previous prime is 21391733747. The next prime is 21391733773. The reversal of 21391733749 is 94733719312.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 13916920900 + 7474812849 = 117970^2 + 86457^2 .

It is a cyclic number.

It is not a de Polignac number, because 21391733749 - 2¹ = 21391733747 is a prime.

Together with 21391733747, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21391733747) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10695866874 + 10695866875.

It is an arithmetic number, because the mean of its divisors is an integer number (10695866875).

Almost surely, 2^21391733749 is an apocalyptic number.

It is an amenable number.

21391733749 is a deficient number, since it is larger than the sum of its proper divisors (1).

21391733749 is an equidigital number, since it uses as much as digits as its factorization.

21391733749 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 857304, while the sum is 49.

The spelling of 21391733749 in words is "twenty-one billion, three hundred ninety-one million, seven hundred thirty-three thousand, seven hundred forty-nine".