21242744 has 8 divisors (see below), whose sum is σ = 39830160. Its totient is φ = 10621368.

The previous prime is 21242729. The next prime is 21242747. The reversal of 21242744 is 44724212.

It is a tau number, because it is divible by the number of its divisors (8).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21242747) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1327664 + ... + 1327679.

It is an arithmetic number, because the mean of its divisors is an integer number (4978770).

Almost surely, 2^21242744 is an apocalyptic number.

It is an amenable number.

21242744 is a deficient number, since it is larger than the sum of its proper divisors (18587416).

21242744 is a wasteful number, since it uses less digits than its factorization.

21242744 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2655349 (or 2655345 counting only the distinct ones).

The product of its digits is 3584, while the sum is 26.

The square root of 21242744 is about 4608.9851377500. The cubic root of 21242744 is about 276.9513831622.

Adding to 21242744 its reverse (44724212), we get a palindrome (65966956).

The spelling of 21242744 in words is "twenty-one million, two hundred forty-two thousand, seven hundred forty-four".