1991867040 has 144 divisors (see below), whose sum is σ = 6810804000. Its totient is φ = 530105856.

The previous prime is 1991867011. The next prime is 1991867047. The reversal of 1991867040 is 407681991.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (144).

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 (1991867047) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 947911 + ... + 950009.

It is an arithmetic number, because the mean of its divisors is an integer number (47297250).

Almost surely, 2^1991867040 is an apocalyptic number.

1991867040 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 1991867040, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (3405402000).

1991867040 is an abundant number, since it is smaller than the sum of its proper divisors (4818936960).

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

1991867040 is a wasteful number, since it uses less digits than its factorization.

1991867040 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2779 (or 2768 counting only the distinct ones).

The product of its (nonzero) digits is 108864, while the sum is 45.

The square root of 1991867040 is about 44630.3376639702. The cubic root of 1991867040 is about 1258.2109151359.

The spelling of 1991867040 in words is "one billion, nine hundred ninety-one million, eight hundred sixty-seven thousand, forty".