21382405 has 16 divisors (see below), whose sum is σ = 28896768. Its totient is φ = 15048000.

The previous prime is 21382393. The next prime is 21382409. The reversal of 21382405 is 50428312.

It is a de Polignac number, because none of the positive numbers 2^k-21382405 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21382405.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21382409) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 4566 + ... + 7975.

It is an arithmetic number, because the mean of its divisors is an integer number (1806048).

Almost surely, 2^21382405 is an apocalyptic number.

It is an amenable number.

21382405 is a deficient number, since it is larger than the sum of its proper divisors (7514363).

21382405 is a wasteful number, since it uses less digits than its factorization.

21382405 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12588.

The product of its (nonzero) digits is 1920, while the sum is 25.

The square root of 21382405 is about 4624.1112659624. Note that the first 3 decimals coincide. The cubic root of 21382405 is about 277.5569993565.

The spelling of 21382405 in words is "twenty-one million, three hundred eighty-two thousand, four hundred five".