21242245 has 4 divisors (see below), whose sum is σ = 25490700. Its totient is φ = 16993792.

The previous prime is 21242237. The next prime is 21242339. The reversal of 21242245 is 54224212.

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 3928324 + 17313921 = 1982^2 + 4161^2 .

It is a cyclic number.

It is not a de Polignac number, because 21242245 - 2³ = 21242237 is a prime.

It is a super-4 number, since 4×21242245⁴ (a number of 30 digits) contains 4444 as substring.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2124220 + ... + 2124229.

It is an arithmetic number, because the mean of its divisors is an integer number (6372675).

Almost surely, 2^21242245 is an apocalyptic number.

It is an amenable number.

21242245 is a deficient number, since it is larger than the sum of its proper divisors (4248455).

21242245 is an equidigital number, since it uses as much as digits as its factorization.

21242245 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4248454.

The product of its digits is 1280, while the sum is 22.

The square root of 21242245 is about 4608.9310040399. The cubic root of 21242245 is about 276.9492145814.

Adding to 21242245 its reverse (54224212), we get a palindrome (75466457).

The spelling of 21242245 in words is "twenty-one million, two hundred forty-two thousand, two hundred forty-five".