19817215749 has 6 divisors (see below), whose sum is σ = 28624867206. Its totient is φ = 13211477160.

The previous prime is 19817215739. The next prime is 19817215787. The reversal of 19817215749 is 94751271891.

It can be written as a sum of positive squares in only one way, i.e., 12846635649 + 6970580100 = 113343^2 + 83490^2 .

It is not a de Polignac number, because 19817215749 - 2⁸ = 19817215493 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 19817215695 and 19817215704.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (19817215739) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1100956422 + ... + 1100956439.

It is an arithmetic number, because the mean of its divisors is an integer number (4770811201).

Almost surely, 2^19817215749 is an apocalyptic number.

It is an amenable number.

19817215749 is a deficient number, since it is larger than the sum of its proper divisors (8807651457).

19817215749 is a wasteful number, since it uses less digits than its factorization.

19817215749 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2201912867 (or 2201912864 counting only the distinct ones).

The product of its digits is 1270080, while the sum is 54.

The spelling of 19817215749 in words is "nineteen billion, eight hundred seventeen million, two hundred fifteen thousand, seven hundred forty-nine".