21551225 has 24 divisors (see below), whose sum is σ = 28644000. Its totient is φ = 16035840.

The previous prime is 21551221. The next prime is 21551251. The reversal of 21551225 is 52215512.

It is not a de Polignac number, because 21551225 - 2² = 21551221 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21551225.

It is not an unprimeable number, because it can be changed into a prime (21551221) 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, 27641 + ... + 28409.

It is an arithmetic number, because the mean of its divisors is an integer number (1193500).

Almost surely, 2^21551225 is an apocalyptic number.

21551225 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21551225 is a deficient number, since it is larger than the sum of its proper divisors (7092775).

21551225 is a wasteful number, since it uses less digits than its factorization.

21551225 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 857 (or 852 counting only the distinct ones).

The product of its digits is 1000, while the sum is 23.

The square root of 21551225 is about 4642.3296953146. The cubic root of 21551225 is about 278.2855484279.

Adding to 21551225 its reverse (52215512), we get a palindrome (73766737).

The spelling of 21551225 in words is "twenty-one million, five hundred fifty-one thousand, two hundred twenty-five".