861994666 has 32 divisors (see below), whose sum is σ = 1443173760. Its totient is φ = 383404224.

The previous prime is 861994663. The next prime is 861994669. The reversal of 861994666 is 666499168.

It is an interprime number because it is at equal distance from previous prime (861994663) and next prime (861994669).

It is not an unprimeable number, because it can be changed into a prime (861994663) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 740601 + ... + 741763.

It is an arithmetic number, because the mean of its divisors is an integer number (45099180).

Almost surely, 2^861994666 is an apocalyptic number.

861994666 is a deficient number, since it is larger than the sum of its proper divisors (581179094).

861994666 is a wasteful number, since it uses less digits than its factorization.

861994666 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2190.

The product of its digits is 3359232, while the sum is 55.

The square root of 861994666 is about 29359.7456732854. The cubic root of 861994666 is about 951.7031924636.

It can be divided in two parts, 8619 and 94666, that added together give a triangular number (103285 = T₄₅₄).

The spelling of 861994666 in words is "eight hundred sixty-one million, nine hundred ninety-four thousand, six hundred sixty-six".