221687 has 4 divisors (see below), whose sum is σ = 227136. Its totient is φ = 216240.

The previous prime is 221677. The next prime is 221707. The reversal of 221687 is 786122.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 221687 - 2⁴ = 221671 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (221657) 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, 2663 + ... + 2744.

It is an arithmetic number, because the mean of its divisors is an integer number (56784).

2²²¹⁶⁸⁷ is an apocalyptic number.

221687 is a deficient number, since it is larger than the sum of its proper divisors (5449).

221687 is an equidigital number, since it uses as much as digits as its factorization.

221687 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5448.

The product of its digits is 1344, while the sum is 26.

The square root of 221687 is about 470.8364896649. The cubic root of 221687 is about 60.5220191690.

The spelling of 221687 in words is "two hundred twenty-one thousand, six hundred eighty-seven".