21645384 has 16 divisors (see below), whose sum is σ = 54113520. Its totient is φ = 7215120.

The previous prime is 21645373. The next prime is 21645413. The reversal of 21645384 is 48354612.

It is a hoax number, since the sum of its digits (33) coincides with the sum of the digits of its distinct prime factors.

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, 450922 + ... + 450969.

It is an arithmetic number, because the mean of its divisors is an integer number (3382095).

Almost surely, 2^21645384 is an apocalyptic number.

21645384 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

21645384 is an abundant number, since it is smaller than the sum of its proper divisors (32468136).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21645384 is a wasteful number, since it uses less digits than its factorization.

21645384 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 901900 (or 901896 counting only the distinct ones).

The product of its digits is 23040, while the sum is 33.

The square root of 21645384 is about 4652.4599944545. The cubic root of 21645384 is about 278.6902434463.

Adding to 21645384 its reverse (48354612), we get a palindrome (69999996).

The spelling of 21645384 in words is "twenty-one million, six hundred forty-five thousand, three hundred eighty-four".