21525405 has 16 divisors (see below), whose sum is σ = 37571904. Its totient is φ = 10436480.

The previous prime is 21525403. The next prime is 21525407. The reversal of 21525405 is 50452512.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (21525403) and next prime (21525407).

It is not a de Polignac number, because 21525405 - 2¹ = 21525403 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21525403) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 65064 + ... + 65393.

It is an arithmetic number, because the mean of its divisors is an integer number (2348244).

Almost surely, 2^21525405 is an apocalyptic number.

It is an amenable number.

21525405 is a deficient number, since it is larger than the sum of its proper divisors (16046499).

21525405 is a wasteful number, since it uses less digits than its factorization.

21525405 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 130476.

The product of its (nonzero) digits is 2000, while the sum is 24.

The square root of 21525405 is about 4639.5479305639. The cubic root of 21525405 is about 278.1743682932.

Adding to 21525405 its reverse (50452512), we get a palindrome (71977917).

It can be divided in two parts, 2152 and 5405, that added together give a palindrome (7557).

The spelling of 21525405 in words is "twenty-one million, five hundred twenty-five thousand, four hundred five".