66503891 has 2 divisors, whose sum is σ = 66503892. Its totient is φ = 66503890.

The previous prime is 66503869. The next prime is 66503893. The reversal of 66503891 is 19830566.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 66503891 - 2¹⁴ = 66487507 is a prime.

Together with 66503893, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (66503893) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33251945 + 33251946.

It is an arithmetic number, because the mean of its divisors is an integer number (33251946).

Almost surely, 2^66503891 is an apocalyptic number.

66503891 is a deficient number, since it is larger than the sum of its proper divisors (1).

66503891 is an equidigital number, since it uses as much as digits as its factorization.

66503891 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 38880, while the sum is 38.

The square root of 66503891 is about 8154.9917841773. The cubic root of 66503891 is about 405.1498525892.

The spelling of 66503891 in words is "sixty-six million, five hundred three thousand, eight hundred ninety-one".