1666611661 has 16 divisors (see below), whose sum is σ = 1959431040. Its totient is φ = 1397517120.

The previous prime is 1666611647. The next prime is 1666611679. The reversal of 1666611661 is 1661166661.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1666611661 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 (1666611601) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 235176 + ... + 242158.

It is an arithmetic number, because the mean of its divisors is an integer number (122464440).

Almost surely, 2^1666611661 is an apocalyptic number.

1666611661 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

1666611661 is a deficient number, since it is larger than the sum of its proper divisors (292819379).

1666611661 is a wasteful number, since it uses less digits than its factorization.

1666611661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8676.

The product of its digits is 46656, while the sum is 40.

The square root of 1666611661 is about 40824.1553617463. The cubic root of 1666611661 is about 1185.6180580674.

The spelling of 1666611661 in words is "one billion, six hundred sixty-six million, six hundred eleven thousand, six hundred sixty-one".