21315213 has 6 divisors (see below), whose sum is σ = 30788654. Its totient is φ = 14210136.

The previous prime is 21315211. The next prime is 21315221. The reversal of 21315213 is 31251312.

It can be written as a sum of positive squares in only one way, i.e., 15468489 + 5846724 = 3933^2 + 2418^2 .

It is not a de Polignac number, because 21315213 - 2¹ = 21315211 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 (21315211) 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 5 ways as a sum of consecutive naturals, for example, 1184170 + ... + 1184187.

Almost surely, 2^21315213 is an apocalyptic number.

It is an amenable number.

21315213 is a deficient number, since it is larger than the sum of its proper divisors (9473441).

21315213 is a wasteful number, since it uses less digits than its factorization.

21315213 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2368363 (or 2368360 counting only the distinct ones).

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

The square root of 21315213 is about 4616.8401531784. The cubic root of 21315213 is about 277.2659628882.

Adding to 21315213 its reverse (31251312), we get a palindrome (52566525).

It can be divided in two parts, 21315 and 213, that added together give a triangular number (21528 = T₂₀₇).

The spelling of 21315213 in words is "twenty-one million, three hundred fifteen thousand, two hundred thirteen".