213121305 has 24 divisors (see below), whose sum is σ = 374929152. Its totient is φ = 111966624.

The previous prime is 213121303. The next prime is 213121313. The reversal of 213121305 is 503121312.

It is not a de Polignac number, because 213121305 - 2¹ = 213121303 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (213121303) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 32329 + ... + 38358.

It is an arithmetic number, because the mean of its divisors is an integer number (15622048).

Almost surely, 2^213121305 is an apocalyptic number.

It is an amenable number.

213121305 is a deficient number, since it is larger than the sum of its proper divisors (161807847).

213121305 is a wasteful number, since it uses less digits than its factorization.

213121305 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 70765 (or 70762 counting only the distinct ones).

The product of its (nonzero) digits is 180, while the sum is 18.

The square root of 213121305 is about 14598.6747686220. The cubic root of 213121305 is about 597.3226120943.

Adding to 213121305 its reverse (503121312), we get a palindrome (716242617).

It can be divided in two parts, 2131 and 21305, that added together give a triangular number (23436 = T₂₁₆).

The spelling of 213121305 in words is "two hundred thirteen million, one hundred twenty-one thousand, three hundred five".