21351443 has 4 divisors (see below), whose sum is σ = 21377328. Its totient is φ = 21325560.

The previous prime is 21351433. The next prime is 21351457. The reversal of 21351443 is 34415312.

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 21351443 - 2¹⁶ = 21285907 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21351413) 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 3 ways as a sum of consecutive naturals, for example, 11663 + ... + 13368.

It is an arithmetic number, because the mean of its divisors is an integer number (5344332).

Almost surely, 2^21351443 is an apocalyptic number.

21351443 is a deficient number, since it is larger than the sum of its proper divisors (25885).

21351443 is an equidigital number, since it uses as much as digits as its factorization.

21351443 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 25884.

The product of its digits is 1440, while the sum is 23.

The square root of 21351443 is about 4620.7621665695. The cubic root of 21351443 is about 277.4229659289.

Adding to 21351443 its reverse (34415312), we get a palindrome (55766755).

The spelling of 21351443 in words is "twenty-one million, three hundred fifty-one thousand, four hundred forty-three".