21387225 has 24 divisors (see below), whose sum is σ = 35569152. Its totient is φ = 11339200.

The previous prime is 21387203. The next prime is 21387227. The reversal of 21387225 is 52278312.

It is not a de Polignac number, because 21387225 - 2⁵ = 21387193 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21387192 and 21387201.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21387227) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 13579 + ... + 15071.

It is an arithmetic number, because the mean of its divisors is an integer number (1482048).

Almost surely, 2^21387225 is an apocalyptic number.

21387225 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21387225 is a deficient number, since it is larger than the sum of its proper divisors (14181927).

21387225 is a wasteful number, since it uses less digits than its factorization.

21387225 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1697 (or 1692 counting only the distinct ones).

The product of its digits is 6720, while the sum is 30.

The square root of 21387225 is about 4624.6324178252. The cubic root of 21387225 is about 277.5778533285.

It can be divided in two parts, 21387 and 225, that added together give a palindrome (21612).

The spelling of 21387225 in words is "twenty-one million, three hundred eighty-seven thousand, two hundred twenty-five".