21540538 has 4 divisors (see below), whose sum is σ = 32310810. Its totient is φ = 10770268.

The previous prime is 21540529. The next prime is 21540551. The reversal of 21540538 is 83504512.

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

It can be written as a sum of positive squares in only one way, i.e., 21095649 + 444889 = 4593^2 + 667^2 .

It is an unprimeable number.

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 as a sum of consecutive naturals, namely, 5385133 + ... + 5385136.

Almost surely, 2^21540538 is an apocalyptic number.

21540538 is a deficient number, since it is larger than the sum of its proper divisors (10770272).

21540538 is a wasteful number, since it uses less digits than its factorization.

21540538 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10770271.

The product of its (nonzero) digits is 4800, while the sum is 28.

The square root of 21540538 is about 4641.1785141276. The cubic root of 21540538 is about 278.2395413078.

The spelling of 21540538 in words is "twenty-one million, five hundred forty thousand, five hundred thirty-eight".