21528625 has 16 divisors (see below), whose sum is σ = 27063504. Its totient is φ = 17097600.

The previous prime is 21528599. The next prime is 21528629. The reversal of 21528625 is 52682512.

It can be written as a sum of positive squares in 8 ways, for example, as 11587216 + 9941409 = 3404^2 + 3153^2 .

It is not a de Polignac number, because 21528625 - 2⁷ = 21528497 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21528629) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 19077 + ... + 20173.

It is an arithmetic number, because the mean of its divisors is an integer number (1691469).

Almost surely, 2^21528625 is an apocalyptic number.

21528625 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21528625 is a deficient number, since it is larger than the sum of its proper divisors (5534879).

21528625 is a wasteful number, since it uses less digits than its factorization.

21528625 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1269 (or 1259 counting only the distinct ones).

The product of its digits is 9600, while the sum is 31.

The square root of 21528625 is about 4639.8949341553. The cubic root of 21528625 is about 278.1882383660.

The spelling of 21528625 in words is "twenty-one million, five hundred twenty-eight thousand, six hundred twenty-five".