21525205 has 24 divisors (see below), whose sum is σ = 28656936. Its totient is φ = 15429120.

The previous prime is 21525199. The next prime is 21525223. The reversal of 21525205 is 50252512.

It can be written as a sum of positive squares in 12 ways, for example, as 13242321 + 8282884 = 3639^2 + 2878^2 .

It is not a de Polignac number, because 21525205 - 2³ = 21525197 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 109167 + ... + 109363.

It is an arithmetic number, because the mean of its divisors is an integer number (1194039).

Almost surely, 2^21525205 is an apocalyptic number.

It is an amenable number.

21525205 is a deficient number, since it is larger than the sum of its proper divisors (7131731).

21525205 is a wasteful number, since it uses less digits than its factorization.

21525205 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 297 (or 256 counting only the distinct ones).

The product of its (nonzero) digits is 1000, while the sum is 22.

The square root of 21525205 is about 4639.5263766898. The cubic root of 21525205 is about 278.1735067524.

Adding to 21525205 its reverse (50252512), we get a palindrome (71777717).

The spelling of 21525205 in words is "twenty-one million, five hundred twenty-five thousand, two hundred five".