191611981 has 8 divisors (see below), whose sum is σ = 221327424. Its totient is φ = 163945920.

The previous prime is 191611969. The next prime is 191611991. The reversal of 191611981 is 189116191.

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 191611981 - 2¹⁷ = 191480909 is a prime.

It is a super-2 number, since 2×191611981² = 73430302525488722, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 191611981.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (191611951) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 512145 + ... + 512518.

It is an arithmetic number, because the mean of its divisors is an integer number (27665928).

Almost surely, 2^191611981 is an apocalyptic number.

191611981 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

191611981 is a deficient number, since it is larger than the sum of its proper divisors (29715443).

191611981 is a wasteful number, since it uses less digits than its factorization.

191611981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1024691.

The product of its digits is 3888, while the sum is 37.

The square root of 191611981 is about 13842.3979497773. The cubic root of 191611981 is about 576.5109408697.

The spelling of 191611981 in words is "one hundred ninety-one million, six hundred eleven thousand, nine hundred eighty-one".