21384405 has 80 divisors (see below), whose sum is σ = 46231680. Its totient is φ = 9237888.

The previous prime is 21384403. The next prime is 21384413. The reversal of 21384405 is 50448312.

21384405 is a `hidden beast` number, since 213 + 8 + 440 + 5 = 666.

It is not a de Polignac number, because 21384405 - 2¹ = 21384403 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21384403) by changing a digit.

It is a polite number, since it can be written in 79 ways as a sum of consecutive naturals, for example, 53667 + ... + 54063.

It is an arithmetic number, because the mean of its divisors is an integer number (577896).

Almost surely, 2^21384405 is an apocalyptic number.

It is an amenable number.

21384405 is an abundant number, since it is smaller than the sum of its proper divisors (24847275).

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

21384405 is a wasteful number, since it uses less digits than its factorization.

21384405 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 440 (or 431 counting only the distinct ones).

The product of its (nonzero) digits is 3840, while the sum is 27.

The square root of 21384405 is about 4624.3275186777. The cubic root of 21384405 is about 277.5656528373.

The spelling of 21384405 in words is "twenty-one million, three hundred eighty-four thousand, four hundred five".