1666611647 has 2 divisors, whose sum is σ = 1666611648. Its totient is φ = 1666611646.

The previous prime is 1666611623. The next prime is 1666611679. The reversal of 1666611647 is 7461166661.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 1666611647 - 2¹⁶ = 1666546111 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 1666611598 and 1666611607.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1666611607) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 833305823 + 833305824.

It is an arithmetic number, because the mean of its divisors is an integer number (833305824).

Almost surely, 2^1666611647 is an apocalyptic number.

1666611647 is a deficient number, since it is larger than the sum of its proper divisors (1).

1666611647 is an equidigital number, since it uses as much as digits as its factorization.

1666611647 is an evil number, because the sum of its binary digits is even.

The product of its digits is 217728, while the sum is 44.

The square root of 1666611647 is about 40824.1551902792. The cubic root of 1666611647 is about 1185.6180547475.

The spelling of 1666611647 in words is "one billion, six hundred sixty-six million, six hundred eleven thousand, six hundred forty-seven".