66820491 has 16 divisors (see below), whose sum is σ = 100249600. Its totient is φ = 43981704.

The previous prime is 66820441. The next prime is 66820513. The reversal of 66820491 is 19402866.

It is not a de Polignac number, because 66820491 - 2⁶ = 66820427 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (66820441) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 13531 + ... + 17796.

It is an arithmetic number, because the mean of its divisors is an integer number (6265600).

Almost surely, 2^66820491 is an apocalyptic number.

66820491 is a deficient number, since it is larger than the sum of its proper divisors (33429109).

66820491 is a wasteful number, since it uses less digits than its factorization.

66820491 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 31415 (or 31409 counting only the distinct ones).

The product of its (nonzero) digits is 20736, while the sum is 36.

The square root of 66820491 is about 8174.3801599877. The cubic root of 66820491 is about 405.7917570399.

The spelling of 66820491 in words is "sixty-six million, eight hundred twenty thousand, four hundred ninety-one".