1991215842 has 64 divisors (see below), whose sum is σ = 5066496000. Its totient is φ = 517193040.

The previous prime is 1991215841. The next prime is 1991215843. The reversal of 1991215842 is 2485121991.

It is an interprime number because it is at equal distance from previous prime (1991215841) and next prime (1991215843).

It is a Harshad number since it is a multiple of its sum of digits (42).

It is a junction number, because it is equal to n+sod(n) for n = 1991215794 and 1991215803.

It is not an unprimeable number, because it can be changed into a prime (1991215841) 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, 21342 + ... + 66617.

It is an arithmetic number, because the mean of its divisors is an integer number (79164000).

Almost surely, 2^1991215842 is an apocalyptic number.

1991215842 is an abundant number, since it is smaller than the sum of its proper divisors (3075280158).

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

1991215842 is a wasteful number, since it uses less digits than its factorization.

1991215842 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 87996 (or 87982 counting only the distinct ones).

The product of its digits is 51840, while the sum is 42.

The square root of 1991215842 is about 44623.0416040861. The cubic root of 1991215842 is about 1258.0737852104.

The spelling of 1991215842 in words is "one billion, nine hundred ninety-one million, two hundred fifteen thousand, eight hundred forty-two".