21215445 has 16 divisors (see below), whose sum is σ = 34055232. Its totient is φ = 11278080.

The previous prime is 21215437. The next prime is 21215449. The reversal of 21215445 is 54451212.

It is not a de Polignac number, because 21215445 - 2³ = 21215437 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21215449) 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 15 ways as a sum of consecutive naturals, for example, 2829 + ... + 7101.

It is an arithmetic number, because the mean of its divisors is an integer number (2128452).

Almost surely, 2^21215445 is an apocalyptic number.

It is an amenable number.

21215445 is a deficient number, since it is larger than the sum of its proper divisors (12839787).

21215445 is a wasteful number, since it uses less digits than its factorization.

21215445 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4612.

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

The square root of 21215445 is about 4606.0226877426. The cubic root of 21215445 is about 276.8326957839.

Adding to 21215445 its reverse (54451212), we get a palindrome (75666657).

The spelling of 21215445 in words is "twenty-one million, two hundred fifteen thousand, four hundred forty-five".