21006742 has 8 divisors (see below), whose sum is σ = 33168600. Its totient is φ = 9950544.

The previous prime is 21006737. The next prime is 21006743. The reversal of 21006742 is 24760012.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21006743) 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, 276367 + ... + 276442.

It is an arithmetic number, because the mean of its divisors is an integer number (4146075).

Almost surely, 2^21006742 is an apocalyptic number.

21006742 is a deficient number, since it is larger than the sum of its proper divisors (12161858).

21006742 is a wasteful number, since it uses less digits than its factorization.

21006742 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 552830.

The product of its (nonzero) digits is 672, while the sum is 22.

The square root of 21006742 is about 4583.3112484316. The cubic root of 21006742 is about 275.9219393470.

Adding to 21006742 its reverse (24760012), we get a palindrome (45766754).

The spelling of 21006742 in words is "twenty-one million, six thousand, seven hundred forty-two".