66640831 has 2 divisors, whose sum is σ = 66640832. Its totient is φ = 66640830.

The previous prime is 66640829. The next prime is 66640859. The reversal of 66640831 is 13804666.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 66640831 - 2¹ = 66640829 is a prime.

It is a super-2 number, since 2×66640831² = 8882000712741122, which contains 22 as substring.

Together with 66640829, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (66640801) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33320415 + 33320416.

It is an arithmetic number, because the mean of its divisors is an integer number (33320416).

Almost surely, 2^66640831 is an apocalyptic number.

66640831 is a deficient number, since it is larger than the sum of its proper divisors (1).

66640831 is an equidigital number, since it uses as much as digits as its factorization.

66640831 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 20736, while the sum is 34.

The square root of 66640831 is about 8163.3835509548. The cubic root of 66640831 is about 405.4277470227.

The spelling of 66640831 in words is "sixty-six million, six hundred forty thousand, eight hundred thirty-one".