19781969 has 2 divisors, whose sum is σ = 19781970. Its totient is φ = 19781968.

The previous prime is 19781963. The next prime is 19781981. The reversal of 19781969 is 96918791.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 16851025 + 2930944 = 4105^2 + 1712^2 .

It is a cyclic number.

It is not a de Polignac number, because 19781969 - 2⁴ = 19781953 is a prime.

It is a super-2 number, since 2×19781969² = 782652595033922, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (19781963) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9890984 + 9890985.

It is an arithmetic number, because the mean of its divisors is an integer number (9890985).

Almost surely, 2^19781969 is an apocalyptic number.

It is an amenable number.

19781969 is a deficient number, since it is larger than the sum of its proper divisors (1).

19781969 is an equidigital number, since it uses as much as digits as its factorization.

19781969 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 244944, while the sum is 50.

The square root of 19781969 is about 4447.6925478275. The cubic root of 19781969 is about 270.4517767945.

The spelling of 19781969 in words is "nineteen million, seven hundred eighty-one thousand, nine hundred sixty-nine".