861651 has 32 divisors (see below), whose sum is σ = 1505280. Its totient is φ = 476928.

The previous prime is 861647. The next prime is 861659. The reversal of 861651 is 156168.

861651 is a `hidden beast` number, since 8 + 6 + 1 + 651 = 666.

It is not a de Polignac number, because 861651 - 2² = 861647 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

Its product of digits (1440) is a multiple of the sum of its prime factors (160).

It is not an unprimeable number, because it can be changed into a prime (861659) 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 31 ways as a sum of consecutive naturals, for example, 8835 + ... + 8931.

It is an arithmetic number, because the mean of its divisors is an integer number (47040).

2⁸⁶¹⁶⁵¹ is an apocalyptic number.

861651 is a deficient number, since it is larger than the sum of its proper divisors (643629).

861651 is a wasteful number, since it uses less digits than its factorization.

861651 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 160 (or 154 counting only the distinct ones).

The product of its digits is 1440, while the sum is 27.

The square root of 861651 is about 928.2515822771. The cubic root of 861651 is about 95.1576698446.

861651 divided by its sum of digits (27) gives a palindrome (31913).

The spelling of 861651 in words is "eight hundred sixty-one thousand, six hundred fifty-one".