19815497591 has 2 divisors, whose sum is σ = 19815497592. Its totient is φ = 19815497590.

The previous prime is 19815497563. The next prime is 19815497599. The reversal of 19815497591 is 19579451891.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 19815497591 - 2¹⁴ = 19815481207 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 19815497591.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (19815497599) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9907748795 + 9907748796.

It is an arithmetic number, because the mean of its divisors is an integer number (9907748796).

Almost surely, 2^19815497591 is an apocalyptic number.

19815497591 is a deficient number, since it is larger than the sum of its proper divisors (1).

19815497591 is an equidigital number, since it uses as much as digits as its factorization.

19815497591 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 4082400, while the sum is 59.

The spelling of 19815497591 in words is "nineteen billion, eight hundred fifteen million, four hundred ninety-seven thousand, five hundred ninety-one".