21215242 has 4 divisors (see below), whose sum is σ = 31822866. Its totient is φ = 10607620.

The previous prime is 21215237. The next prime is 21215261. The reversal of 21215242 is 24251212.

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

It can be written as a sum of positive squares in only one way, i.e., 20421361 + 793881 = 4519^2 + 891^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5303809 + ... + 5303812.

Almost surely, 2^21215242 is an apocalyptic number.

21215242 is a deficient number, since it is larger than the sum of its proper divisors (10607624).

21215242 is a wasteful number, since it uses less digits than its factorization.

21215242 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10607623.

The product of its digits is 320, while the sum is 19.

The square root of 21215242 is about 4606.0006513243. Note that the first 3 decimals coincide. The cubic root of 21215242 is about 276.8318128231.

Adding to 21215242 its reverse (24251212), we get a palindrome (45466454).

The spelling of 21215242 in words is "twenty-one million, two hundred fifteen thousand, two hundred forty-two".