1966765591 has 4 divisors (see below), whose sum is σ = 2247732112. Its totient is φ = 1685799072.

The previous prime is 1966765553. The next prime is 1966765597. The reversal of 1966765591 is 1955676691.

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 1966765591 - 2⁹ = 1966765079 is a prime.

It is a super-3 number, since 3×1966765591³ (a number of 29 digits) contains 333 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1966765597) 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, 140483250 + ... + 140483263.

It is an arithmetic number, because the mean of its divisors is an integer number (561933028).

Almost surely, 2^1966765591 is an apocalyptic number.

1966765591 is a deficient number, since it is larger than the sum of its proper divisors (280966521).

1966765591 is an equidigital number, since it uses as much as digits as its factorization.

1966765591 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 280966520.

The product of its digits is 3061800, while the sum is 55.

The square root of 1966765591 is about 44348.2309793750. The cubic root of 1966765591 is about 1252.9032444635.

Subtracting from 1966765591 its reverse (1955676691), we obtain a square (11088900 = 3330²).

It can be divided in two parts, 19667 and 65591, that added together give a palindrome (85258).

The spelling of 1966765591 in words is "one billion, nine hundred sixty-six million, seven hundred sixty-five thousand, five hundred ninety-one".