19871591 has 2 divisors, whose sum is σ = 19871592. Its totient is φ = 19871590.

The previous prime is 19871573. The next prime is 19871603. The reversal of 19871591 is 19517891.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-19871591 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (19871531) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9935795 + 9935796.

It is an arithmetic number, because the mean of its divisors is an integer number (9935796).

Almost surely, 2^19871591 is an apocalyptic number.

19871591 is a deficient number, since it is larger than the sum of its proper divisors (1).

19871591 is an equidigital number, since it uses as much as digits as its factorization.

19871591 is an evil number, because the sum of its binary digits is even.

The product of its digits is 22680, while the sum is 41.

The square root of 19871591 is about 4457.7562741810. The cubic root of 19871591 is about 270.8595878506.

The spelling of 19871591 in words is "nineteen million, eight hundred seventy-one thousand, five hundred ninety-one".