21768443 has 4 divisors (see below), whose sum is σ = 21782208. Its totient is φ = 21754680.

The previous prime is 21768431. The next prime is 21768457. The reversal of 21768443 is 34486712.

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

It is a cyclic number.

It is not a de Polignac number, because 21768443 - 2¹⁶ = 21702907 is a prime.

It is a super-2 number, since 2×21768443² = 947730221288498, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21768343) by changing a digit.

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, 4148 + ... + 7793.

It is an arithmetic number, because the mean of its divisors is an integer number (5445552).

Almost surely, 2^21768443 is an apocalyptic number.

21768443 is a deficient number, since it is larger than the sum of its proper divisors (13765).

21768443 is a wasteful number, since it uses less digits than its factorization.

21768443 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13764.

The product of its digits is 32256, while the sum is 35.

The square root of 21768443 is about 4665.6664047058. Note that the first 3 decimals coincide. The cubic root of 21768443 is about 279.2173851663.

The spelling of 21768443 in words is "twenty-one million, seven hundred sixty-eight thousand, four hundred forty-three".