1991867760 has 200 divisors, whose sum is σ = 6967857600. Its totient is φ = 527344128.

The previous prime is 1991867749. The next prime is 1991867771. The reversal of 1991867760 is 677681991.

It is an interprime number because it is at equal distance from previous prime (1991867749) and next prime (1991867771).

It is a Harshad number since it is a multiple of its sum of digits (54).

It is a junction number, because it is equal to n+sod(n) for n = 1991867697 and 1991867706.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 964489 + ... + 966551.

It is an arithmetic number, because the mean of its divisors is an integer number (34839288).

Almost surely, 2^1991867760 is an apocalyptic number.

1991867760 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 1991867760, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (3483928800).

1991867760 is an abundant number, since it is smaller than the sum of its proper divisors (4975989840).

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

1991867760 is a wasteful number, since it uses less digits than its factorization.

1991867760 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2237 (or 2222 counting only the distinct ones).

The product of its (nonzero) digits is 1143072, while the sum is 54.

The square root of 1991867760 is about 44630.3457302316. The cubic root of 1991867760 is about 1258.2110667377.

It can be divided in two parts, 19918 and 67760, that added together give a palindrome (87678).

The spelling of 1991867760 in words is "one billion, nine hundred ninety-one million, eight hundred sixty-seven thousand, seven hundred sixty".