213991 has 8 divisors (see below), whose sum is σ = 227520. Its totient is φ = 200928.

The previous prime is 213989. The next prime is 214003. The reversal of 213991 is 199312.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 213991 - 2¹ = 213989 is a prime.

It is an Ulam 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 (213901) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1285 + ... + 1441.

It is an arithmetic number, because the mean of its divisors is an integer number (28440).

2²¹³⁹⁹¹ is an apocalyptic number.

213991 is a deficient number, since it is larger than the sum of its proper divisors (13529).

213991 is a wasteful number, since it uses less digits than its factorization.

213991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 233.

The product of its digits is 486, while the sum is 25.

The square root of 213991 is about 462.5916125483. The cubic root of 213991 is about 59.8134017681.

The spelling of 213991 in words is "two hundred thirteen thousand, nine hundred ninety-one".