19890649 has 2 divisors, whose sum is σ = 19890650. Its totient is φ = 19890648.

The previous prime is 19890643. The next prime is 19890671. The reversal of 19890649 is 94609891.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17808400 + 2082249 = 4220^2 + 1443^2 .

It is an emirp because it is prime and its reverse (94609891) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 19890649 - 2³ = 19890641 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 19890599 and 19890608.

It is not a weakly prime, because it can be changed into another prime (19890641) 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, 9945324 + 9945325.

It is an arithmetic number, because the mean of its divisors is an integer number (9945325).

Almost surely, 2^19890649 is an apocalyptic number.

It is an amenable number.

19890649 is a deficient number, since it is larger than the sum of its proper divisors (1).

19890649 is an equidigital number, since it uses as much as digits as its factorization.

19890649 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 139968, while the sum is 46.

The square root of 19890649 is about 4459.8933843759. The cubic root of 19890649 is about 270.9461501641.

The spelling of 19890649 in words is "nineteen million, eight hundred ninety thousand, six hundred forty-nine".