21525487 has 4 divisors (see below), whose sum is σ = 21574960. Its totient is φ = 21476016.

The previous prime is 21525481. The next prime is 21525529. The reversal of 21525487 is 78452512.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21525487 - 2³ = 21525479 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 (21525481) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 24078 + ... + 24955.

It is an arithmetic number, because the mean of its divisors is an integer number (5393740).

Almost surely, 2^21525487 is an apocalyptic number.

21525487 is a deficient number, since it is larger than the sum of its proper divisors (49473).

21525487 is an equidigital number, since it uses as much as digits as its factorization.

21525487 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 49472.

The product of its digits is 22400, while the sum is 34.

The square root of 21525487 is about 4639.5567676234. The cubic root of 21525487 is about 278.1747215234.

Adding to 21525487 its reverse (78452512), we get a palindrome (99977999).

Subtracting 21525487 from its reverse (78452512), we obtain a square (56927025 = 7545²).

It can be divided in two parts, 215 and 25487, that multiplied together give a triangular number (5479705 = T₃₃₁₀).

The spelling of 21525487 in words is "twenty-one million, five hundred twenty-five thousand, four hundred eighty-seven".