19966649 has 2 divisors, whose sum is σ = 19966650. Its totient is φ = 19966648.

The previous prime is 19966633. The next prime is 19966651. The reversal of 19966649 is 94666991.

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., 13875625 + 6091024 = 3725^2 + 2468^2 .

It is a cyclic number.

It is not a de Polignac number, because 19966649 - 2⁴ = 19966633 is a prime.

Together with 19966651, 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 = 19966597 and 19966606.

It is not a weakly prime, because it can be changed into another prime (19966679) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9983324 + 9983325.

It is an arithmetic number, because the mean of its divisors is an integer number (9983325).

Almost surely, 2^19966649 is an apocalyptic number.

It is an amenable number.

19966649 is a deficient number, since it is larger than the sum of its proper divisors (1).

19966649 is an equidigital number, since it uses as much as digits as its factorization.

19966649 is an evil number, because the sum of its binary digits is even.

The product of its digits is 629856, while the sum is 50.

The square root of 19966649 is about 4468.4056440749. The cubic root of 19966649 is about 271.2907968113.

The spelling of 19966649 in words is "nineteen million, nine hundred sixty-six thousand, six hundred forty-nine".