19645650991 has 2 divisors, whose sum is σ = 19645650992. Its totient is φ = 19645650990.

The previous prime is 19645650977. The next prime is 19645651007. The reversal of 19645650991 is 19905654691.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 19645650991 - 2²³ = 19637262383 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (19645650961) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9822825495 + 9822825496.

It is an arithmetic number, because the mean of its divisors is an integer number (9822825496).

Almost surely, 2^19645650991 is an apocalyptic number.

19645650991 is a deficient number, since it is larger than the sum of its proper divisors (1).

19645650991 is an equidigital number, since it uses as much as digits as its factorization.

19645650991 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2624400, while the sum is 55.

The spelling of 19645650991 in words is "nineteen billion, six hundred forty-five million, six hundred fifty thousand, nine hundred ninety-one".