21521524 has 12 divisors (see below), whose sum is σ = 39878244. Its totient is φ = 10127744.

The previous prime is 21521503. The next prime is 21521527. The reversal of 21521524 is 42512512.

It can be written as a sum of positive squares in 2 ways, for example, as 6451600 + 15069924 = 2540^2 + 3882^2 .

It is a junction number, because it is equal to n+sod(n) for n = 21521495 and 21521504.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21521527) 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, 158179 + ... + 158314.

It is an arithmetic number, because the mean of its divisors is an integer number (3323187).

Almost surely, 2^21521524 is an apocalyptic number.

It is an amenable number.

21521524 is a deficient number, since it is larger than the sum of its proper divisors (18356720).

21521524 is a wasteful number, since it uses less digits than its factorization.

21521524 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 316514 (or 316512 counting only the distinct ones).

The product of its digits is 800, while the sum is 22.

The square root of 21521524 is about 4639.1296597530. The cubic root of 21521524 is about 278.1576491403.

The spelling of 21521524 in words is "twenty-one million, five hundred twenty-one thousand, five hundred twenty-four".