21645304 has 8 divisors (see below), whose sum is σ = 40584960. Its totient is φ = 10822648.

The previous prime is 21645287. The next prime is 21645307. The reversal of 21645304 is 40354612.

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

It is a plaindrome in base 11.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21645307) by changing a digit.

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 as a sum of consecutive naturals, namely, 1352824 + ... + 1352839.

It is an arithmetic number, because the mean of its divisors is an integer number (5073120).

Almost surely, 2^21645304 is an apocalyptic number.

It is an amenable number.

21645304 is a deficient number, since it is larger than the sum of its proper divisors (18939656).

21645304 is a wasteful number, since it uses less digits than its factorization.

21645304 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2705669 (or 2705665 counting only the distinct ones).

The product of its (nonzero) digits is 2880, while the sum is 25.

The square root of 21645304 is about 4652.4513968445. The cubic root of 21645304 is about 278.6899001052.

Adding to 21645304 its reverse (40354612), we get a palindrome (61999916).

The spelling of 21645304 in words is "twenty-one million, six hundred forty-five thousand, three hundred four".