1991387340 has 144 divisors (see below), whose sum is σ = 6395581920. Its totient is φ = 500152320.

The previous prime is 1991387309. The next prime is 1991387347. The reversal of 1991387340 is 437831991.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is not an unprimeable number, because it can be changed into a prime (1991387347) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 617412 + ... + 620628.

Almost surely, 2^1991387340 is an apocalyptic number.

1991387340 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 1991387340, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (3197790960).

1991387340 is an abundant number, since it is smaller than the sum of its proper divisors (4404194580).

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

1991387340 is a wasteful number, since it uses less digits than its factorization.

1991387340 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3432 (or 3427 counting only the distinct ones).

The product of its (nonzero) digits is 163296, while the sum is 45.

The square root of 1991387340 is about 44624.9631932621. The cubic root of 1991387340 is about 1258.1099023303.

The spelling of 1991387340 in words is "one billion, nine hundred ninety-one million, three hundred eighty-seven thousand, three hundred forty".