66856507 has 2 divisors, whose sum is σ = 66856508. Its totient is φ = 66856506.

The previous prime is 66856399. The next prime is 66856523. The reversal of 66856507 is 70565866.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-66856507 is a prime.

It is not a weakly prime, because it can be changed into another prime (66856577) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33428253 + 33428254.

It is an arithmetic number, because the mean of its divisors is an integer number (33428254).

Almost surely, 2^66856507 is an apocalyptic number.

66856507 is a deficient number, since it is larger than the sum of its proper divisors (1).

66856507 is an equidigital number, since it uses as much as digits as its factorization.

66856507 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 302400, while the sum is 43.

The square root of 66856507 is about 8176.5828437068. The cubic root of 66856507 is about 405.8646507021.

It can be divided in two parts, 668 and 56507, that added together give a palindrome (57175).

The spelling of 66856507 in words is "sixty-six million, eight hundred fifty-six thousand, five hundred seven".