21523442 has 16 divisors (see below), whose sum is σ = 33264000. Its totient is φ = 10438560.

The previous prime is 21523433. The next prime is 21523499. The reversal of 21523442 is 24432512.

It is a happy number.

It is an unprimeable number.

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 7 ways as a sum of consecutive naturals, for example, 15659 + ... + 16977.

It is an arithmetic number, because the mean of its divisors is an integer number (2079000).

Almost surely, 2^21523442 is an apocalyptic number.

21523442 is a deficient number, since it is larger than the sum of its proper divisors (11740558).

21523442 is a wasteful number, since it uses less digits than its factorization.

21523442 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1561.

The product of its digits is 1920, while the sum is 23.

The square root of 21523442 is about 4639.3363749571. The cubic root of 21523442 is about 278.1659120391.

Adding to 21523442 its reverse (24432512), we get a palindrome (45955954).

The spelling of 21523442 in words is "twenty-one million, five hundred twenty-three thousand, four hundred forty-two".