215961 has 4 divisors (see below), whose sum is σ = 287952. Its totient is φ = 143972.

The previous prime is 215959. The next prime is 215981. The reversal of 215961 is 169512.

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 215961 - 2¹ = 215959 is a prime.

It is a D-number.

It is a plaindrome in base 14.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 215961.

It is not an unprimeable number, because it can be changed into a prime (215921) 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, 35991 + ... + 35996.

It is an arithmetic number, because the mean of its divisors is an integer number (71988).

2²¹⁵⁹⁶¹ is an apocalyptic number.

It is an amenable number.

215961 is a deficient number, since it is larger than the sum of its proper divisors (71991).

215961 is an equidigital number, since it uses as much as digits as its factorization.

215961 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 71990.

The product of its digits is 540, while the sum is 24.

The square root of 215961 is about 464.7160423312. The cubic root of 215961 is about 59.9963886715.

It can be divided in two parts, 215 and 961, that added together give a triangular number (1176 = T₄₈).

The spelling of 215961 in words is "two hundred fifteen thousand, nine hundred sixty-one".