21006642 has 8 divisors (see below), whose sum is σ = 42013296. Its totient is φ = 7002212.

The previous prime is 21006641. The next prime is 21006673. The reversal of 21006642 is 24660012.

It is a happy number.

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

21006642 is an admirable number.

It is not an unprimeable number, because it can be changed into a prime (21006641) 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, 1750548 + ... + 1750559.

It is an arithmetic number, because the mean of its divisors is an integer number (5251662).

Almost surely, 2^21006642 is an apocalyptic number.

21006642 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21006642 is a wasteful number, since it uses less digits than its factorization.

21006642 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3501112.

The product of its (nonzero) digits is 576, while the sum is 21.

The square root of 21006642 is about 4583.3003392752. The cubic root of 21006642 is about 275.9215015155.

Adding to 21006642 its reverse (24660012), we get a palindrome (45666654).

The spelling of 21006642 in words is "twenty-one million, six thousand, six hundred forty-two".