21438653 has 4 divisors (see below), whose sum is σ = 21802080. Its totient is φ = 21075228.

The previous prime is 21438647. The next prime is 21438673. The reversal of 21438653 is 35683412.

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 21438653 - 2⁶ = 21438589 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 (21438623) 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, 181625 + ... + 181742.

It is an arithmetic number, because the mean of its divisors is an integer number (5450520).

Almost surely, 2^21438653 is an apocalyptic number.

It is an amenable number.

21438653 is a deficient number, since it is larger than the sum of its proper divisors (363427).

21438653 is an equidigital number, since it uses as much as digits as its factorization.

21438653 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 363426.

The product of its digits is 17280, while the sum is 32.

The square root of 21438653 is about 4630.1893049853. The cubic root of 21438653 is about 277.8001643410.

The spelling of 21438653 in words is "twenty-one million, four hundred thirty-eight thousand, six hundred fifty-three".