21605384 has 16 divisors (see below), whose sum is σ = 40718700. Its totient is φ = 10747072.

The previous prime is 21605369. The next prime is 21605399. The reversal of 21605384 is 48350612.

It is an interprime number because it is at equal distance from previous prime (21605369) and next prime (21605399).

It can be written as a sum of positive squares in 2 ways, for example, as 16176484 + 5428900 = 4022^2 + 2330^2 .

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5279 + ... + 8430.

Almost surely, 2^21605384 is an apocalyptic number.

It is an amenable number.

21605384 is a deficient number, since it is larger than the sum of its proper divisors (19113316).

21605384 is a wasteful number, since it uses less digits than its factorization.

21605384 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13912 (or 13908 counting only the distinct ones).

The product of its (nonzero) digits is 5760, while the sum is 29.

The square root of 21605384 is about 4648.1592055350. The cubic root of 21605384 is about 278.5184672744.

Adding to 21605384 its reverse (48350612), we get a palindrome (69955996).

The spelling of 21605384 in words is "twenty-one million, six hundred five thousand, three hundred eighty-four".