19978769 has 2 divisors, whose sum is σ = 19978770. Its totient is φ = 19978768.

The previous prime is 19978753. The next prime is 19978771. The reversal of 19978769 is 96787991.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 13542400 + 6436369 = 3680^2 + 2537^2 .

It is an emirp because it is prime and its reverse (96787991) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 19978769 - 2⁴ = 19978753 is a prime.

It is a super-2 number, since 2×19978769² = 798302421510722, which contains 22 as substring.

Together with 19978771, 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 (19978169) by changing a digit.

It is a good prime.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9989384 + 9989385.

It is an arithmetic number, because the mean of its divisors is an integer number (9989385).

Almost surely, 2^19978769 is an apocalyptic number.

It is an amenable number.

19978769 is a deficient number, since it is larger than the sum of its proper divisors (1).

19978769 is an equidigital number, since it uses as much as digits as its factorization.

19978769 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1714608, while the sum is 56.

The square root of 19978769 is about 4469.7616267537. The cubic root of 19978769 is about 271.3456779849.

The spelling of 19978769 in words is "nineteen million, nine hundred seventy-eight thousand, seven hundred sixty-nine".