1981169691 has 16 divisors (see below), whose sum is σ = 2784848640. Its totient is φ = 1249348320.

The previous prime is 1981169677. The next prime is 1981169737. The reversal of 1981169691 is 1969611891.

It is a happy number.

It is not a de Polignac number, because 1981169691 - 2⁷ = 1981169563 is a prime.

It is not an unprimeable number, because it can be changed into a prime (1981168691) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 11386 + ... + 63968.

It is an arithmetic number, because the mean of its divisors is an integer number (174053040).

Almost surely, 2^1981169691 is an apocalyptic number.

1981169691 is a deficient number, since it is larger than the sum of its proper divisors (803678949).

1981169691 is a wasteful number, since it uses less digits than its factorization.

1981169691 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 53266.

The product of its digits is 209952, while the sum is 51.

The square root of 1981169691 is about 44510.3324072063. The cubic root of 1981169691 is about 1255.9544579194.

The spelling of 1981169691 in words is "one billion, nine hundred eighty-one million, one hundred sixty-nine thousand, six hundred ninety-one".