21606542 has 4 divisors (see below), whose sum is σ = 32409816. Its totient is φ = 10803270.

The previous prime is 21606523. The next prime is 21606547. The reversal of 21606542 is 24560612.

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 (21606547) 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, 5401634 + ... + 5401637.

It is an arithmetic number, because the mean of its divisors is an integer number (8102454).

Almost surely, 2^21606542 is an apocalyptic number.

21606542 is a deficient number, since it is larger than the sum of its proper divisors (10803274).

21606542 is a wasteful number, since it uses less digits than its factorization.

21606542 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10803273.

The product of its (nonzero) digits is 2880, while the sum is 26.

The square root of 21606542 is about 4648.2837693067. The cubic root of 21606542 is about 278.5234431733.

The spelling of 21606542 in words is "twenty-one million, six hundred six thousand, five hundred forty-two".