851666 has 16 divisors (see below), whose sum is σ = 1391256. Its totient is φ = 389376.

The previous prime is 851659. The next prime is 851671. The reversal of 851666 is 666158.

Added to its reverse (666158) it gives a square (1517824 = 1232²).

851666 = T₃₀₈ + T₃₀₉ + ... + T₃₂₄.

It can be written as a sum of positive squares in 4 ways, for example, as 758641 + 93025 = 871^2 + 305^2 .

It is an unprimeable number.

851666 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 920 + ... + 1596.

2⁸⁵¹⁶⁶⁶ is an apocalyptic number.

851666 is a deficient number, since it is larger than the sum of its proper divisors (539590).

851666 is a wasteful number, since it uses less digits than its factorization.

851666 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 733.

The product of its digits is 8640, while the sum is 32.

The square root of 851666 is about 922.8575187969. The cubic root of 851666 is about 94.7886715204.

Adding to 851666 its reverse (666158), we get a square (1517824 = 1232²).

The spelling of 851666 in words is "eight hundred fifty-one thousand, six hundred sixty-six".