1982091991 has 4 divisors (see below), whose sum is σ = 2162282184. Its totient is φ = 1801901800.

The previous prime is 1982091929. The next prime is 1982092111. The reversal of 1982091991 is 1991902891.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 1982091991 - 2²⁷ = 1847874263 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1982091901) 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, 90095080 + ... + 90095101.

It is an arithmetic number, because the mean of its divisors is an integer number (540570546).

Almost surely, 2^1982091991 is an apocalyptic number.

1982091991 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

1982091991 is a deficient number, since it is larger than the sum of its proper divisors (180190193).

1982091991 is a wasteful number, since it uses less digits than its factorization.

1982091991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 180190192.

The product of its (nonzero) digits is 104976, while the sum is 49.

The square root of 1982091991 is about 44520.6917174475. The cubic root of 1982091991 is about 1256.1493237934.

The spelling of 1982091991 in words is "one billion, nine hundred eighty-two million, ninety-one thousand, nine hundred ninety-one".