21405613 has 8 divisors (see below), whose sum is σ = 21843360. Its totient is φ = 20970480.

The previous prime is 21405611. The next prime is 21405619. The reversal of 21405613 is 31650412.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21405613 - 2¹ = 21405611 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 (21405611) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 26806 + ... + 27592.

It is an arithmetic number, because the mean of its divisors is an integer number (2730420).

Almost surely, 2^21405613 is an apocalyptic number.

It is an amenable number.

21405613 is a deficient number, since it is larger than the sum of its proper divisors (437747).

21405613 is an equidigital number, since it uses as much as digits as its factorization.

21405613 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1307.

The product of its (nonzero) digits is 720, while the sum is 22.

The square root of 21405613 is about 4626.6200405912. The cubic root of 21405613 is about 277.6573811695.

The spelling of 21405613 in words is "twenty-one million, four hundred five thousand, six hundred thirteen".