21523456 has 22 divisors (see below), whose sum is σ = 43027940. Its totient is φ = 10761216.

The previous prime is 21523433. The next prime is 21523499. The reversal of 21523456 is 65432512.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9486 + ... + 11533.

Almost surely, 2^21523456 is an apocalyptic number.

It is an amenable number.

21523456 is a deficient number, since it is larger than the sum of its proper divisors (21504484).

21523456 is an equidigital number, since it uses as much as digits as its factorization.

21523456 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21039 (or 21021 counting only the distinct ones).

The product of its digits is 7200, while the sum is 28.

The square root of 21523456 is about 4639.3378837933. The cubic root of 21523456 is about 278.1659723504.

Adding to 21523456 its reverse (65432512), we get a palindrome (86955968).

The spelling of 21523456 in words is "twenty-one million, five hundred twenty-three thousand, four hundred fifty-six".