21538574 has 4 divisors (see below), whose sum is σ = 32307864. Its totient is φ = 10769286.

The previous prime is 21538567. The next prime is 21538579. The reversal of 21538574 is 47583512.

It is a happy number.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21538579) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5384642 + ... + 5384645.

It is an arithmetic number, because the mean of its divisors is an integer number (8076966).

Almost surely, 2^21538574 is an apocalyptic number.

21538574 is a deficient number, since it is larger than the sum of its proper divisors (10769290).

21538574 is a wasteful number, since it uses less digits than its factorization.

21538574 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10769289.

The product of its digits is 33600, while the sum is 35.

The square root of 21538574 is about 4640.9669251138. The cubic root of 21538574 is about 278.2310847090.

The spelling of 21538574 in words is "twenty-one million, five hundred thirty-eight thousand, five hundred seventy-four".