1991779067 has 4 divisors (see below), whose sum is σ = 1991880336. Its totient is φ = 1991677800.

The previous prime is 1991779043. The next prime is 1991779081. The reversal of 1991779067 is 7609771991.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 7609771991 = 151 ⋅50395841.

It is a cyclic number.

It is not a de Polignac number, because 1991779067 - 2¹² = 1991774971 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1991779037) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 10559 + ... + 63992.

It is an arithmetic number, because the mean of its divisors is an integer number (497970084).

Almost surely, 2^1991779067 is an apocalyptic number.

1991779067 is a deficient number, since it is larger than the sum of its proper divisors (101269).

1991779067 is an equidigital number, since it uses as much as digits as its factorization.

1991779067 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 101268.

The product of its (nonzero) digits is 1500282, while the sum is 56.

The square root of 1991779067 is about 44629.3520790970. The cubic root of 1991779067 is about 1258.1923914399.

The spelling of 1991779067 in words is "one billion, nine hundred ninety-one million, seven hundred seventy-nine thousand, sixty-seven".