21312584 has 8 divisors (see below), whose sum is σ = 39961110. Its totient is φ = 10656288.

The previous prime is 21312539. The next prime is 21312587. The reversal of 21312584 is 48521312.

It can be written as a sum of positive squares in only one way, i.e., 12180100 + 9132484 = 3490^2 + 3022^2 .

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

It is not an unprimeable number, because it can be changed into a prime (21312587) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1332029 + ... + 1332044.

Almost surely, 2^21312584 is an apocalyptic number.

It is an amenable number.

21312584 is a deficient number, since it is larger than the sum of its proper divisors (18648526).

21312584 is a wasteful number, since it uses less digits than its factorization.

21312584 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2664079 (or 2664075 counting only the distinct ones).

The product of its digits is 1920, while the sum is 26.

The square root of 21312584 is about 4616.5554258559. Note that the first 3 decimals coincide. The cubic root of 21312584 is about 277.2545631713.

Adding to 21312584 its reverse (48521312), we get a palindrome (69833896).

The spelling of 21312584 in words is "twenty-one million, three hundred twelve thousand, five hundred eighty-four".