1591986991 has 32 divisors (see below), whose sum is σ = 1977131520. Its totient is φ = 1251417600.

The previous prime is 1591986983. The next prime is 1591987003. The reversal of 1591986991 is 1996891951.

It is a cyclic number.

It is not a de Polignac number, because 1591986991 - 2³ = 1591986983 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1591986971) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 745996 + ... + 748126.

It is an arithmetic number, because the mean of its divisors is an integer number (61785360).

Almost surely, 2^1591986991 is an apocalyptic number.

1591986991 is a deficient number, since it is larger than the sum of its proper divisors (385144529).

1591986991 is a wasteful number, since it uses less digits than its factorization.

1591986991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2335.

The product of its digits is 1574640, while the sum is 58.

The square root of 1591986991 is about 39899.7116656249. The cubic root of 1591986991 is about 1167.6513116648.

The spelling of 1591986991 in words is "one billion, five hundred ninety-one million, nine hundred eighty-six thousand, nine hundred ninety-one".