21212045 has 4 divisors (see below), whose sum is σ = 25454460. Its totient is φ = 16969632.

The previous prime is 21212033. The next prime is 21212071. The reversal of 21212045 is 54021212.

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

It can be written as a sum of positive squares in 2 ways, for example, as 12432676 + 8779369 = 3526^2 + 2963^2 .

It is a cyclic number.

It is not a de Polignac number, because 21212045 - 2²⁰ = 20163469 is a prime.

It is a congruent number.

It is an unprimeable number.

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, 2121200 + ... + 2121209.

It is an arithmetic number, because the mean of its divisors is an integer number (6363615).

Almost surely, 2^21212045 is an apocalyptic number.

It is an amenable number.

21212045 is a deficient number, since it is larger than the sum of its proper divisors (4242415).

21212045 is an equidigital number, since it uses as much as digits as its factorization.

21212045 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4242414.

The product of its (nonzero) digits is 160, while the sum is 17.

The square root of 21212045 is about 4605.6535909684. The cubic root of 21212045 is about 276.8179065356.

Adding to 21212045 its reverse (54021212), we get a palindrome (75233257).

The spelling of 21212045 in words is "twenty-one million, two hundred twelve thousand, forty-five".