21123616 has 24 divisors (see below), whose sum is σ = 42060060. Its totient is φ = 10441728.

The previous prime is 21123607. The next prime is 21123631. The reversal of 21123616 is 61632112.

It can be written as a sum of positive squares in 2 ways, for example, as 21123216 + 400 = 4596^2 + 20^2 .

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 in 3 ways as a sum of consecutive naturals, for example, 861 + ... + 6556.

Almost surely, 2^21123616 is an apocalyptic number.

It is an amenable number.

21123616 is a deficient number, since it is larger than the sum of its proper divisors (20936444).

21123616 is an equidigital number, since it uses as much as digits as its factorization.

21123616 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7516 (or 7508 counting only the distinct ones).

The product of its digits is 432, while the sum is 22.

The square root of 21123616 is about 4596.0435158949. The cubic root of 21123616 is about 276.4327036098.

Adding to 21123616 its reverse (61632112), we get a palindrome (82755728).

The spelling of 21123616 in words is "twenty-one million, one hundred twenty-three thousand, six hundred sixteen".