861521 has 4 divisors (see below), whose sum is σ = 889344. Its totient is φ = 833700.

The previous prime is 861499. The next prime is 861541. The reversal of 861521 is 125168.

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 a cyclic number.

It is not a de Polignac number, because 861521 - 2¹⁴ = 845137 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (861541) 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, 13865 + ... + 13926.

It is an arithmetic number, because the mean of its divisors is an integer number (222336).

2⁸⁶¹⁵²¹ is an apocalyptic number.

It is an amenable number.

861521 is a deficient number, since it is larger than the sum of its proper divisors (27823).

861521 is a wasteful number, since it uses less digits than its factorization.

861521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 27822.

The product of its digits is 480, while the sum is 23.

The square root of 861521 is about 928.1815555159. The cubic root of 861521 is about 95.1528840248.

Adding to 861521 its reverse (125168), we get a palindrome (986689).

The spelling of 861521 in words is "eight hundred sixty-one thousand, five hundred twenty-one".