21445521 has 8 divisors (see below), whose sum is σ = 29516544. Its totient is φ = 13835760.

The previous prime is 21445513. The next prime is 21445537. The reversal of 21445521 is 12554412.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21445521 - 2³ = 21445513 is a prime.

It is a super-2 number, since 2×21445521² = 919820741922882, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21445491 and 21445500.

It is not an unprimeable number, because it can be changed into a prime (21445511) 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 7 ways as a sum of consecutive naturals, for example, 115206 + ... + 115391.

It is an arithmetic number, because the mean of its divisors is an integer number (3689568).

Almost surely, 2^21445521 is an apocalyptic number.

It is an amenable number.

21445521 is a deficient number, since it is larger than the sum of its proper divisors (8071023).

21445521 is a wasteful number, since it uses less digits than its factorization.

21445521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 230631.

The product of its digits is 1600, while the sum is 24.

The square root of 21445521 is about 4630.9308999379. The cubic root of 21445521 is about 277.8298261521.

Adding to 21445521 its reverse (12554412), we get a palindrome (33999933).

The spelling of 21445521 in words is "twenty-one million, four hundred forty-five thousand, five hundred twenty-one".