21438817 has 4 divisors (see below), whose sum is σ = 21697200. Its totient is φ = 21180436.

The previous prime is 21438793. The next prime is 21438827. The reversal of 21438817 is 71883412.

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 21438817 - 2⁷ = 21438689 is a prime.

It is a Duffinian number.

It is a plaindrome in base 11.

It is not an unprimeable number, because it can be changed into a prime (21438827) 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, 129067 + ... + 129232.

It is an arithmetic number, because the mean of its divisors is an integer number (5424300).

Almost surely, 2^21438817 is an apocalyptic number.

It is an amenable number.

21438817 is a deficient number, since it is larger than the sum of its proper divisors (258383).

21438817 is an equidigital number, since it uses as much as digits as its factorization.

21438817 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 258382.

The product of its digits is 10752, while the sum is 34.

The square root of 21438817 is about 4630.2070148105. The cubic root of 21438817 is about 277.8008727050.

The spelling of 21438817 in words is "twenty-one million, four hundred thirty-eight thousand, eight hundred seventeen".