21125213 has 4 divisors (see below), whose sum is σ = 21140448. Its totient is φ = 21109980.

The previous prime is 21125183. The next prime is 21125219. The reversal of 21125213 is 31252112.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21125213 - 2¹⁶ = 21059677 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21125191 and 21125200.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21125219) 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 3 ways as a sum of consecutive naturals, for example, 5303 + ... + 8388.

It is an arithmetic number, because the mean of its divisors is an integer number (5285112).

Almost surely, 2^21125213 is an apocalyptic number.

It is an amenable number.

21125213 is a deficient number, since it is larger than the sum of its proper divisors (15235).

21125213 is a wasteful number, since it uses less digits than its factorization.

21125213 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15234.

The product of its digits is 120, while the sum is 17.

The square root of 21125213 is about 4596.2172489994. The cubic root of 21125213 is about 276.4396697767.

Adding to 21125213 its reverse (31252112), we get a palindrome (52377325).

The spelling of 21125213 in words is "twenty-one million, one hundred twenty-five thousand, two hundred thirteen".