21145564 has 24 divisors (see below), whose sum is σ = 40748400. Its totient is φ = 9521280.

The previous prime is 21145559. The next prime is 21145583. The reversal of 21145564 is 46554112.

It is a congruent 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, 2592 + ... + 7000.

It is an arithmetic number, because the mean of its divisors is an integer number (1697850).

Almost surely, 2^21145564 is an apocalyptic number.

It is an amenable number.

21145564 is a deficient number, since it is larger than the sum of its proper divisors (19602836).

21145564 is a wasteful number, since it uses less digits than its factorization.

21145564 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4533 (or 4531 counting only the distinct ones).

The product of its digits is 4800, while the sum is 28.

The square root of 21145564 is about 4598.4306018467. The cubic root of 21145564 is about 276.5284107855.

Adding to 21145564 its reverse (46554112), we get a palindrome (67699676).

The spelling of 21145564 in words is "twenty-one million, one hundred forty-five thousand, five hundred sixty-four".