21987304 has 8 divisors (see below), whose sum is σ = 41226210. Its totient is φ = 10993648.

The previous prime is 21987299. The next prime is 21987331. The reversal of 21987304 is 40378912.

It can be written as a sum of positive squares in only one way, i.e., 14424804 + 7562500 = 3798^2 + 2750^2 .

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

It is a self number, because there is not a number n which added to its sum of digits gives 21987304.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1374199 + ... + 1374214.

Almost surely, 2^21987304 is an apocalyptic number.

It is an amenable number.

21987304 is a deficient number, since it is larger than the sum of its proper divisors (19238906).

21987304 is a wasteful number, since it uses less digits than its factorization.

21987304 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2748419 (or 2748415 counting only the distinct ones).

The product of its (nonzero) digits is 12096, while the sum is 34.

The square root of 21987304 is about 4689.0621663612. The cubic root of 21987304 is about 280.1500216461.

The spelling of 21987304 in words is "twenty-one million, nine hundred eighty-seven thousand, three hundred four".