21528225 has 36 divisors (see below), whose sum is σ = 38862096. Its totient is φ = 11391840.

The previous prime is 21528223. The next prime is 21528257. The reversal of 21528225 is 52282512.

It is not a de Polignac number, because 21528225 - 2¹ = 21528223 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21528223) by changing a digit.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 36382 + ... + 36968.

Almost surely, 2^21528225 is an apocalyptic number.

21528225 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21528225 is a deficient number, since it is larger than the sum of its proper divisors (17333871).

21528225 is a wasteful number, since it uses less digits than its factorization.

21528225 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 766 (or 758 counting only the distinct ones).

The product of its digits is 3200, while the sum is 27.

The square root of 21528225 is about 4639.8518295308. The cubic root of 21528225 is about 278.1865154508.

The spelling of 21528225 in words is "twenty-one million, five hundred twenty-eight thousand, two hundred twenty-five".