66321791 has 4 divisors (see below), whose sum is σ = 66487584. Its totient is φ = 66156000.

The previous prime is 66321779. The next prime is 66321793. The reversal of 66321791 is 19712366.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 19712366 = 2 ⋅9856183.

It is a cyclic number.

It is not a de Polignac number, because 66321791 - 2⁶ = 66321727 is a prime.

It is a super-2 number, since 2×66321791² = 8797159922895362, which contains 22 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 (66321793) 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, 82295 + ... + 83096.

It is an arithmetic number, because the mean of its divisors is an integer number (16621896).

Almost surely, 2^66321791 is an apocalyptic number.

66321791 is a deficient number, since it is larger than the sum of its proper divisors (165793).

66321791 is a wasteful number, since it uses less digits than its factorization.

66321791 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 165792.

The product of its digits is 13608, while the sum is 35.

The square root of 66321791 is about 8143.8191900361. The cubic root of 66321791 is about 404.7797227178.

The spelling of 66321791 in words is "sixty-six million, three hundred twenty-one thousand, seven hundred ninety-one".