21536542 has 4 divisors (see below), whose sum is σ = 32304816. Its totient is φ = 10768270.

The previous prime is 21536539. The next prime is 21536549. The reversal of 21536542 is 24563512.

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

It is a self number, because there is not a number n which added to its sum of digits gives 21536542.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21536549) 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 as a sum of consecutive naturals, namely, 5384134 + ... + 5384137.

It is an arithmetic number, because the mean of its divisors is an integer number (8076204).

Almost surely, 2^21536542 is an apocalyptic number.

21536542 is a deficient number, since it is larger than the sum of its proper divisors (10768274).

21536542 is a wasteful number, since it uses less digits than its factorization.

21536542 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10768273.

The product of its digits is 7200, while the sum is 28.

The square root of 21536542 is about 4640.7480000534. The cubic root of 21536542 is about 278.2223347743. Note that the first 3 decimals are identical.

The spelling of 21536542 in words is "twenty-one million, five hundred thirty-six thousand, five hundred forty-two".