1991591610 has 32 divisors (see below), whose sum is σ = 4860838080. Its totient is φ = 522089088.

The previous prime is 1991591593. The next prime is 1991591611. The reversal of 1991591610 is 161951991.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (1991591611) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 560827 + ... + 564366.

It is an arithmetic number, because the mean of its divisors is an integer number (151901190).

Almost surely, 2^1991591610 is an apocalyptic number.

1991591610 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

1991591610 is an abundant number, since it is smaller than the sum of its proper divisors (2869246470).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

1991591610 is a wasteful number, since it uses less digits than its factorization.

1991591610 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1125262.

The product of its (nonzero) digits is 21870, while the sum is 42.

The square root of 1991591610 is about 44627.2518759558. The cubic root of 1991591610 is about 1258.1529184591.

The spelling of 1991591610 in words is "one billion, nine hundred ninety-one million, five hundred ninety-one thousand, six hundred ten".