861999 has 4 divisors (see below), whose sum is σ = 1149336. Its totient is φ = 574664.

The previous prime is 861997. The next prime is 862009. The reversal of 861999 is 999168.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 861999 - 2¹ = 861997 is a prime.

It is a D-number.

861999 is a modest number, since divided by 999 gives 861 as remainder.

It is a self number, because there is not a number n which added to its sum of digits gives 861999.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 861999.

It is not an unprimeable number, because it can be changed into a prime (861997) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 143664 + ... + 143669.

It is an arithmetic number, because the mean of its divisors is an integer number (287334).

2⁸⁶¹⁹⁹⁹ is an apocalyptic number.

861999 is a deficient number, since it is larger than the sum of its proper divisors (287337).

861999 is a wasteful number, since it uses less digits than its factorization.

861999 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 287336.

The product of its digits is 34992, while the sum is 42.

The square root of 861999 is about 928.4390125366. The cubic root of 861999 is about 95.1704787475.

The spelling of 861999 in words is "eight hundred sixty-one thousand, nine hundred ninety-nine".