861399 has 36 divisors (see below), whose sum is σ = 1576848. Its totient is φ = 443520.

The previous prime is 861391. The next prime is 861433. The reversal of 861399 is 993168.

It is not a de Polignac number, because 861399 - 2³ = 861391 is a prime.

861399 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (861391) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 7567 + ... + 7679.

2⁸⁶¹³⁹⁹ is an apocalyptic number.

861399 is a deficient number, since it is larger than the sum of its proper divisors (715449).

861399 is a wasteful number, since it uses less digits than its factorization.

With its successor (861400) it forms a Ruth-Aaron pair, since the sum of their prime factors is the same (148).

861399 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 148 (or 134 counting only the distinct ones).

The product of its digits is 11664, while the sum is 36.

The square root of 861399 is about 928.1158332881. The cubic root of 861399 is about 95.1483922791.

Subtracting 861399 from its reverse (993168), we obtain a square (131769 = 363²).

It can be divided in two parts, 86 and 1399, that added together give a triangular number (1485 = T₅₄).

The spelling of 861399 in words is "eight hundred sixty-one thousand, three hundred ninety-nine".