21571225 has 12 divisors (see below), whose sum is σ = 28806316. Its totient is φ = 15929280.

The previous prime is 21571169. The next prime is 21571229. The reversal of 21571225 is 52217512.

It can be written as a sum of positive squares in 6 ways, for example, as 4489 + 21566736 = 67^2 + 4644^2 .

It is not a de Polignac number, because 21571225 - 2¹³ = 21563033 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (25).

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 21571225.

It is not an unprimeable number, because it can be changed into a prime (21571229) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 32862 + ... + 33511.

Almost surely, 2^21571225 is an apocalyptic number.

21571225 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21571225 is a deficient number, since it is larger than the sum of its proper divisors (7235091).

21571225 is a wasteful number, since it uses less digits than its factorization.

21571225 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 66396 (or 66391 counting only the distinct ones).

The product of its digits is 1400, while the sum is 25.

The square root of 21571225 is about 4644.4832866531. The cubic root of 21571225 is about 278.3716068021.

Adding to 21571225 its reverse (52217512), we get a palindrome (73788737).

The spelling of 21571225 in words is "twenty-one million, five hundred seventy-one thousand, two hundred twenty-five".