21768242 has 4 divisors (see below), whose sum is σ = 32652366. Its totient is φ = 10884120.

The previous prime is 21768223. The next prime is 21768251. The reversal of 21768242 is 24286712.

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., 14145121 + 7623121 = 3761^2 + 2761^2 .

It is a junction number, because it is equal to n+sod(n) for n = 21768199 and 21768208.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5442059 + ... + 5442062.

Almost surely, 2^21768242 is an apocalyptic number.

21768242 is a deficient number, since it is larger than the sum of its proper divisors (10884124).

21768242 is a wasteful number, since it uses less digits than its factorization.

21768242 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10884123.

The product of its digits is 10752, while the sum is 32.

The square root of 21768242 is about 4665.6448643248. The cubic root of 21768242 is about 279.2165257745.

The spelling of 21768242 in words is "twenty-one million, seven hundred sixty-eight thousand, two hundred forty-two".