21521443 has 4 divisors (see below), whose sum is σ = 21640528. Its totient is φ = 21402360.

The previous prime is 21521431. The next prime is 21521453. The reversal of 21521443 is 34412512.

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 21521443 - 2⁹ = 21520931 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21521413) 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, 59271 + ... + 59632.

It is an arithmetic number, because the mean of its divisors is an integer number (5410132).

Almost surely, 2^21521443 is an apocalyptic number.

21521443 is a deficient number, since it is larger than the sum of its proper divisors (119085).

21521443 is a wasteful number, since it uses less digits than its factorization.

21521443 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 119084.

The product of its digits is 960, while the sum is 22.

The square root of 21521443 is about 4639.1209296590. The cubic root of 21521443 is about 278.1573001749.

Adding to 21521443 its reverse (34412512), we get a palindrome (55933955).

The spelling of 21521443 in words is "twenty-one million, five hundred twenty-one thousand, four hundred forty-three".