21457225 has 12 divisors (see below), whose sum is σ = 27327244. Its totient is φ = 16701120.

The previous prime is 21457207. The next prime is 21457253. The reversal of 21457225 is 52275412.

It can be written as a sum of positive squares in 6 ways, for example, as 1279161 + 20178064 = 1131^2 + 4492^2 .

It is not a de Polignac number, because 21457225 - 2⁵ = 21457193 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21457193 and 21457202.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 10674 + ... + 12523.

Almost surely, 2^21457225 is an apocalyptic number.

21457225 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21457225 is a deficient number, since it is larger than the sum of its proper divisors (5870019).

21457225 is a wasteful number, since it uses less digits than its factorization.

21457225 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 23244 (or 23239 counting only the distinct ones).

The product of its digits is 5600, while the sum is 28.

The square root of 21457225 is about 4632.1944043833. The cubic root of 21457225 is about 277.8803592978.

The spelling of 21457225 in words is "twenty-one million, four hundred fifty-seven thousand, two hundred twenty-five".