1991615836 has 48 divisors (see below), whose sum is σ = 4094399232. Its totient is φ = 829872000.

The previous prime is 1991615831. The next prime is 1991615849. The reversal of 1991615836 is 6385161991.

It is a self number, because there is not a number n which added to its sum of digits gives 1991615836.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1991615831) 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, 349611 + ... + 355261.

It is an arithmetic number, because the mean of its divisors is an integer number (85299984).

Almost surely, 2^1991615836 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 1991615836, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2047199616).

1991615836 is an abundant number, since it is smaller than the sum of its proper divisors (2102783396).

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

1991615836 is a wasteful number, since it uses less digits than its factorization.

1991615836 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6010 (or 6008 counting only the distinct ones).

The product of its digits is 349920, while the sum is 49.

The square root of 1991615836 is about 44627.5233012095. The cubic root of 1991615836 is about 1258.1580198880.

The spelling of 1991615836 in words is "one billion, nine hundred ninety-one million, six hundred fifteen thousand, eight hundred thirty-six".