21444387 has 4 divisors (see below), whose sum is σ = 28592520. Its totient is φ = 14296256.

The previous prime is 21444373. The next prime is 21444389. The reversal of 21444387 is 78344412.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21444387 - 2⁶ = 21444323 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21444389) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3574062 + ... + 3574067.

It is an arithmetic number, because the mean of its divisors is an integer number (7148130).

Almost surely, 2^21444387 is an apocalyptic number.

21444387 is a deficient number, since it is larger than the sum of its proper divisors (7148133).

21444387 is an equidigital number, since it uses as much as digits as its factorization.

21444387 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7148132.

The product of its digits is 21504, while the sum is 33.

The square root of 21444387 is about 4630.8084607334. The cubic root of 21444387 is about 277.8249290211.

Adding to 21444387 its reverse (78344412), we get a palindrome (99788799).

The spelling of 21444387 in words is "twenty-one million, four hundred forty-four thousand, three hundred eighty-seven".