665666 has 16 divisors (see below), whose sum is σ = 1080000. Its totient is φ = 306768.

The previous prime is 665659. The next prime is 665677. The reversal of 665666 is 666566.

665666 = T₂₂₉ + T₂₃₀ + ... + T₂₅₁.

665666 = 230² + 231² + ... + 241².

It is a super-2 number, since 2×665666² = 886222447112, which contains 22 as substring.

It is a Curzon number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1085 + ... + 1583.

It is an arithmetic number, because the mean of its divisors is an integer number (67500).

2⁶⁶⁵⁶⁶⁶ is an apocalyptic number.

665666 is a deficient number, since it is larger than the sum of its proper divisors (414334).

665666 is a wasteful number, since it uses less digits than its factorization.

665666 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 553.

The product of its digits is 38880, while the sum is 35.

The square root of 665666 is about 815.8835701251. The cubic root of 665666 is about 87.3143164441.

Subtracting 665666 from its reverse (666566), we obtain a square (900 = 30²).

It can be divided in two parts, 665 and 666, that added together give a palindrome (1331).

The spelling of 665666 in words is "six hundred sixty-five thousand, six hundred sixty-six".