19781369 has 2 divisors, whose sum is σ = 19781370. Its totient is φ = 19781368.

The previous prime is 19781327. The next prime is 19781371. The reversal of 19781369 is 96318791.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 13227769 + 6553600 = 3637^2 + 2560^2 .

It is an emirp because it is prime and its reverse (96318791) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 19781369 - 2¹⁶ = 19715833 is a prime.

It is a super-2 number, since 2×19781369² = 782605119028322, which contains 22 as substring.

Together with 19781371, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (19781269) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9890684 + 9890685.

It is an arithmetic number, because the mean of its divisors is an integer number (9890685).

Almost surely, 2^19781369 is an apocalyptic number.

It is an amenable number.

19781369 is a deficient number, since it is larger than the sum of its proper divisors (1).

19781369 is an equidigital number, since it uses as much as digits as its factorization.

19781369 is an evil number, because the sum of its binary digits is even.

The product of its digits is 81648, while the sum is 44.

The square root of 19781369 is about 4447.6250966105. The cubic root of 19781369 is about 270.4490424407.

The spelling of 19781369 in words is "nineteen million, seven hundred eighty-one thousand, three hundred sixty-nine".