213021 has 6 divisors (see below), whose sum is σ = 307710. Its totient is φ = 142008.

The previous prime is 213019. The next prime is 213023. The reversal of 213021 is 120312.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (213019) and next prime (213023).

It can be written as a sum of positive squares in only one way, i.e., 168921 + 44100 = 411^2 + 210^2 .

It is not a de Polignac number, because 213021 - 2¹ = 213019 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (9), and also a Moran number because the ratio is a prime number: 23669 = 213021 / (2 + 1 + 3 + 0 + 2 + 1).

It is a plaindrome in base 14.

It is a junction number, because it is equal to n+sod(n) for n = 212994 and 213012.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (213023) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 11826 + ... + 11843.

It is an arithmetic number, because the mean of its divisors is an integer number (51285).

2²¹³⁰²¹ is an apocalyptic number.

It is an amenable number.

213021 is a deficient number, since it is larger than the sum of its proper divisors (94689).

213021 is a wasteful number, since it uses less digits than its factorization.

213021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 23675 (or 23672 counting only the distinct ones).

The product of its (nonzero) digits is 12, while the sum is 9.

The square root of 213021 is about 461.5419807558. The cubic root of 213021 is about 59.7228887933.

Adding to 213021 its reverse (120312), we get a palindrome (333333).

The spelling of 213021 in words is "two hundred thirteen thousand, twenty-one".