66401663 has 4 divisors (see below), whose sum is σ = 66444840. Its totient is φ = 66358488.

The previous prime is 66401653. The next prime is 66401669. The reversal of 66401663 is 36610466.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 36610466 = 2 ⋅18305233.

It is a cyclic number.

It is not a de Polignac number, because 66401663 - 2⁸ = 66401407 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66401669) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 19193 + ... + 22386.

It is an arithmetic number, because the mean of its divisors is an integer number (16611210).

Almost surely, 2^66401663 is an apocalyptic number.

66401663 is a deficient number, since it is larger than the sum of its proper divisors (43177).

66401663 is a wasteful number, since it uses less digits than its factorization.

66401663 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 43176.

The product of its (nonzero) digits is 15552, while the sum is 32.

The square root of 66401663 is about 8148.7215561706. The cubic root of 66401663 is about 404.9421509611.

The spelling of 66401663 in words is "sixty-six million, four hundred one thousand, six hundred sixty-three".