21252405 has 16 divisors (see below), whose sum is σ = 34251840. Its totient is φ = 11251968.

The previous prime is 21252403. The next prime is 21252433. The reversal of 21252405 is 50425212.

It is a happy number.

It is not a de Polignac number, because 21252405 - 2¹ = 21252403 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21252401) 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, 3012 + ... + 7181.

It is an arithmetic number, because the mean of its divisors is an integer number (2140740).

Almost surely, 2^21252405 is an apocalyptic number.

It is an amenable number.

21252405 is a deficient number, since it is larger than the sum of its proper divisors (12999435).

21252405 is a wasteful number, since it uses less digits than its factorization.

21252405 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10340.

The product of its (nonzero) digits is 800, while the sum is 21.

The square root of 21252405 is about 4610.0330801416. The cubic root of 21252405 is about 276.9933617597.

Adding to 21252405 its reverse (50425212), we get a palindrome (71677617).

The spelling of 21252405 in words is "twenty-one million, two hundred fifty-two thousand, four hundred five".