21645613 has 8 divisors (see below), whose sum is σ = 23848416. Its totient is φ = 19482000.

The previous prime is 21645551. The next prime is 21645619. The reversal of 21645613 is 31654612.

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 21645613 - 2⁹ = 21645101 is a prime.

It is a Duffinian number.

It is a plaindrome in base 8.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21645619) 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 7 ways as a sum of consecutive naturals, for example, 8631 + ... + 10852.

It is an arithmetic number, because the mean of its divisors is an integer number (2981052).

Almost surely, 2^21645613 is an apocalyptic number.

It is an amenable number.

21645613 is a deficient number, since it is larger than the sum of its proper divisors (2202803).

21645613 is a wasteful number, since it uses less digits than its factorization.

21645613 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 19595.

The product of its digits is 4320, while the sum is 28.

The square root of 21645613 is about 4652.4846050256. The cubic root of 21645613 is about 278.6912262554.

It can be divided in two parts, 2164 and 5613, that added together give a palindrome (7777).

The spelling of 21645613 in words is "twenty-one million, six hundred forty-five thousand, six hundred thirteen".