19449786821 has 2 divisors, whose sum is σ = 19449786822. Its totient is φ = 19449786820.

The previous prime is 19449786767. The next prime is 19449786827. The reversal of 19449786821 is 12868794491.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 11896264900 + 7553521921 = 109070^2 + 86911^2 .

It is a cyclic number.

It is not a de Polignac number, because 19449786821 - 2¹⁴ = 19449770437 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (19449786827) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9724893410 + 9724893411.

It is an arithmetic number, because the mean of its divisors is an integer number (9724893411).

Almost surely, 2^19449786821 is an apocalyptic number.

It is an amenable number.

19449786821 is a deficient number, since it is larger than the sum of its proper divisors (1).

19449786821 is an equidigital number, since it uses as much as digits as its factorization.

19449786821 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 6967296, while the sum is 59.

The spelling of 19449786821 in words is "nineteen billion, four hundred forty-nine million, seven hundred eighty-six thousand, eight hundred twenty-one".