863661 has 4 divisors (see below), whose sum is σ = 1151552. Its totient is φ = 575772.

The previous prime is 863641. The next prime is 863671. The reversal of 863661 is 166368.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 863661 - 2¹¹ = 861613 is a prime.

It is a D-number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (863641) 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, 143941 + ... + 143946.

It is an arithmetic number, because the mean of its divisors is an integer number (287888).

2⁸⁶³⁶⁶¹ is an apocalyptic number.

It is an amenable number.

863661 is a deficient number, since it is larger than the sum of its proper divisors (287891).

863661 is a wasteful number, since it uses less digits than its factorization.

863661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 287890.

The product of its digits is 5184, while the sum is 30.

The square root of 863661 is about 929.3336322333. Note that the first 3 decimals coincide. The cubic root of 863661 is about 95.2316047998.

The spelling of 863661 in words is "eight hundred sixty-three thousand, six hundred sixty-one".