1565166661 has 2 divisors, whose sum is σ = 1565166662. Its totient is φ = 1565166660.

The previous prime is 1565166623. The next prime is 1565166703. The reversal of 1565166661 is 1666615651.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1544961636 + 20205025 = 39306^2 + 4495^2 .

It is a cyclic number.

It is not a de Polignac number, because 1565166661 - 2¹⁵ = 1565133893 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1565163661) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 782583330 + 782583331.

It is an arithmetic number, because the mean of its divisors is an integer number (782583331).

Almost surely, 2^1565166661 is an apocalyptic number.

It is an amenable number.

1565166661 is a deficient number, since it is larger than the sum of its proper divisors (1).

1565166661 is an equidigital number, since it uses as much as digits as its factorization.

1565166661 is an evil number, because the sum of its binary digits is even.

The product of its digits is 194400, while the sum is 43.

The square root of 1565166661 is about 39562.1872625870. The cubic root of 1565166661 is about 1161.0569688916.

The spelling of 1565166661 in words is "one billion, five hundred sixty-five million, one hundred sixty-six thousand, six hundred sixty-one".