21345556 has 12 divisors (see below), whose sum is σ = 37439668. Its totient is φ = 10648512.

The previous prime is 21345539. The next prime is 21345589. The reversal of 21345556 is 65554312.

It can be written as a sum of positive squares in 2 ways, for example, as 18352656 + 2992900 = 4284^2 + 1730^2 .

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4011 + ... + 7666.

Almost surely, 2^21345556 is an apocalyptic number.

It is an amenable number.

21345556 is a deficient number, since it is larger than the sum of its proper divisors (16094112).

21345556 is a wasteful number, since it uses less digits than its factorization.

21345556 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12138 (or 12136 counting only the distinct ones).

The product of its digits is 18000, while the sum is 31.

The square root of 21345556 is about 4620.1251065312. The cubic root of 21345556 is about 277.3974666512.

Adding to 21345556 its reverse (65554312), we get a palindrome (86899868).

The spelling of 21345556 in words is "twenty-one million, three hundred forty-five thousand, five hundred fifty-six".