19644779851 has 2 divisors, whose sum is σ = 19644779852. Its totient is φ = 19644779850.

The previous prime is 19644779813. The next prime is 19644779867. The reversal of 19644779851 is 15897744691.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 19644779851 - 2¹⁹ = 19644255563 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 19644779851.

It is not a weakly prime, because it can be changed into another prime (19644770851) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9822389925 + 9822389926.

It is an arithmetic number, because the mean of its divisors is an integer number (9822389926).

Almost surely, 2^19644779851 is an apocalyptic number.

19644779851 is a deficient number, since it is larger than the sum of its proper divisors (1).

19644779851 is an equidigital number, since it uses as much as digits as its factorization.

19644779851 is an evil number, because the sum of its binary digits is even.

The product of its digits is 15240960, while the sum is 61.

The spelling of 19644779851 in words is "nineteen billion, six hundred forty-four million, seven hundred seventy-nine thousand, eight hundred fifty-one".