212921 has 4 divisors (see below), whose sum is σ = 214500. Its totient is φ = 211344.

The previous prime is 212917. The next prime is 212923. The reversal of 212921 is 129212.

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

It can be written as a sum of positive squares in 2 ways, for example, as 19321 + 193600 = 139^2 + 440^2 .

It is a cyclic number.

It is not a de Polignac number, because 212921 - 2² = 212917 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 212921.

It is not an unprimeable number, because it can be changed into a prime (212923) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 566 + ... + 863.

It is an arithmetic number, because the mean of its divisors is an integer number (53625).

2²¹²⁹²¹ is an apocalyptic number.

It is an amenable number.

212921 is a deficient number, since it is larger than the sum of its proper divisors (1579).

212921 is a wasteful number, since it uses less digits than its factorization.

212921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1578.

The product of its digits is 72, while the sum is 17.

The square root of 212921 is about 461.4336355317. The cubic root of 212921 is about 59.7135419470.

The spelling of 212921 in words is "two hundred twelve thousand, nine hundred twenty-one".