1991109901 has 8 divisors (see below), whose sum is σ = 2184256800. Its totient is φ = 1799985840.

The previous prime is 1991109877. The next prime is 1991109919. The reversal of 1991109901 is 1099011991.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 1991109901 - 2²⁵ = 1957555469 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1991109941) by changing a digit.

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 7 ways as a sum of consecutive naturals, for example, 503646 + ... + 507583.

It is an arithmetic number, because the mean of its divisors is an integer number (273032100).

Almost surely, 2^1991109901 is an apocalyptic number.

1991109901 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

1991109901 is the 19956-th centered decagonal number.

It is an amenable number.

1991109901 is a deficient number, since it is larger than the sum of its proper divisors (193146899).

1991109901 is a wasteful number, since it uses less digits than its factorization.

1991109901 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1011419.

The product of its (nonzero) digits is 6561, while the sum is 40.

The square root of 1991109901 is about 44621.8545221957. The cubic root of 1991109901 is about 1258.0514732212.

The spelling of 1991109901 in words is "one billion, nine hundred ninety-one million, one hundred nine thousand, nine hundred one".