21606413 has 4 divisors (see below), whose sum is σ = 21816288. Its totient is φ = 21396540.

The previous prime is 21606359. The next prime is 21606419. The reversal of 21606413 is 31460612.

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 21606413 - 2²⁴ = 4829197 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 (21606419) 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, 104783 + ... + 104988.

It is an arithmetic number, because the mean of its divisors is an integer number (5454072).

Almost surely, 2^21606413 is an apocalyptic number.

It is an amenable number.

21606413 is a deficient number, since it is larger than the sum of its proper divisors (209875).

21606413 is a wasteful number, since it uses less digits than its factorization.

21606413 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 209874.

The product of its (nonzero) digits is 864, while the sum is 23.

The square root of 21606413 is about 4648.2698931968. The cubic root of 21606413 is about 278.5228888721.

The spelling of 21606413 in words is "twenty-one million, six hundred six thousand, four hundred thirteen".