21389413 has 4 divisors (see below), whose sum is σ = 21911148. Its totient is φ = 20867680.

The previous prime is 21389393. The next prime is 21389419. The reversal of 21389413 is 31498312.

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 2362369 + 19027044 = 1537^2 + 4362^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21389413 is a prime.

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21389419) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 260806 + ... + 260887.

It is an arithmetic number, because the mean of its divisors is an integer number (5477787).

Almost surely, 2^21389413 is an apocalyptic number.

It is an amenable number.

21389413 is a deficient number, since it is larger than the sum of its proper divisors (521735).

21389413 is an equidigital number, since it uses as much as digits as its factorization.

21389413 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 521734.

The product of its digits is 5184, while the sum is 31.

The square root of 21389413 is about 4624.8689711169. The cubic root of 21389413 is about 277.5873187864.

The spelling of 21389413 in words is "twenty-one million, three hundred eighty-nine thousand, four hundred thirteen".