861555 has 16 divisors (see below), whose sum is σ = 1451520. Its totient is φ = 435168.

The previous prime is 861551. The next prime is 861559. The reversal of 861555 is 555168.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (861551) and next prime (861559).

It is not a de Polignac number, because 861555 - 2² = 861551 is a prime.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 861555.

It is not an unprimeable number, because it can be changed into a prime (861551) 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 15 ways as a sum of consecutive naturals, for example, 1227 + ... + 1796.

It is an arithmetic number, because the mean of its divisors is an integer number (90720).

2⁸⁶¹⁵⁵⁵ is an apocalyptic number.

861555 is a deficient number, since it is larger than the sum of its proper divisors (589965).

861555 is a wasteful number, since it uses less digits than its factorization.

861555 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3050.

The product of its digits is 6000, while the sum is 30.

The square root of 861555 is about 928.1998707175. The cubic root of 861555 is about 95.1541357473.

The spelling of 861555 in words is "eight hundred sixty-one thousand, five hundred fifty-five".