21225172 has 6 divisors (see below), whose sum is σ = 37144058. Its totient is φ = 10612584.

The previous prime is 21225121. The next prime is 21225179. The reversal of 21225172 is 27152212.

It can be written as a sum of positive squares in only one way, i.e., 15397776 + 5827396 = 3924^2 + 2414^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21225179) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2653143 + ... + 2653150.

Almost surely, 2^21225172 is an apocalyptic number.

It is an amenable number.

21225172 is a deficient number, since it is larger than the sum of its proper divisors (15918886).

21225172 is a wasteful number, since it uses less digits than its factorization.

21225172 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5306297 (or 5306295 counting only the distinct ones).

The product of its digits is 560, while the sum is 22.

The square root of 21225172 is about 4607.0784668812. The cubic root of 21225172 is about 276.8749973588.

Adding to 21225172 its reverse (27152212), we get a palindrome (48377384).

The spelling of 21225172 in words is "twenty-one million, two hundred twenty-five thousand, one hundred seventy-two".