210861 has 12 divisors (see below), whose sum is σ = 348192. Its totient is φ = 120456.

The previous prime is 210857. The next prime is 210869. The reversal of 210861 is 168012.

It is not a de Polignac number, because 210861 - 2² = 210857 is a prime.

It is a super-2 number, since 2×210861² = 88924722642, which contains 22 as substring.

It is a plaindrome in base 16.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (210869) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 1611 + ... + 1736.

It is an arithmetic number, because the mean of its divisors is an integer number (29016).

2²¹⁰⁸⁶¹ is an apocalyptic number.

210861 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

210861 is a deficient number, since it is larger than the sum of its proper divisors (137331).

210861 is a wasteful number, since it uses less digits than its factorization.

210861 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3360 (or 3357 counting only the distinct ones).

The product of its (nonzero) digits is 96, while the sum is 18.

The square root of 210861 is about 459.1960365683. The cubic root of 210861 is about 59.5203423606.

Adding to 210861 its reverse (168012), we get a palindrome (378873).

Subtracting from 210861 its reverse (168012), we obtain a square (42849 = 207²).

The spelling of 210861 in words is "two hundred ten thousand, eight hundred sixty-one".