21817142 has 4 divisors (see below), whose sum is σ = 32725716. Its totient is φ = 10908570.

The previous prime is 21817141. The next prime is 21817153. The reversal of 21817142 is 24171812.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21817141) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5454284 + ... + 5454287.

It is an arithmetic number, because the mean of its divisors is an integer number (8181429).

Almost surely, 2^21817142 is an apocalyptic number.

21817142 is a deficient number, since it is larger than the sum of its proper divisors (10908574).

21817142 is a wasteful number, since it uses less digits than its factorization.

21817142 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10908573.

The product of its digits is 896, while the sum is 26.

The square root of 21817142 is about 4670.8823577564. The cubic root of 21817142 is about 279.4254459835.

Adding to 21817142 its reverse (24171812), we get a palindrome (45988954).

The spelling of 21817142 in words is "twenty-one million, eight hundred seventeen thousand, one hundred forty-two".