21206744 has 16 divisors (see below), whose sum is σ = 42821520. Its totient is φ = 9787680.

The previous prime is 21206699. The next prime is 21206747. The reversal of 21206744 is 44760212.

It is a Smith number, since the sum of its digits (26) coincides with the sum of the digits of its prime factors.

It is a Harshad number since it is a multiple of its sum of digits (26).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21206747) 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, 101852 + ... + 102059.

It is an arithmetic number, because the mean of its divisors is an integer number (2676345).

Almost surely, 2^21206744 is an apocalyptic number.

It is an amenable number.

21206744 is an abundant number, since it is smaller than the sum of its proper divisors (21614776).

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

21206744 is a wasteful number, since it uses less digits than its factorization.

21206744 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 203930 (or 203926 counting only the distinct ones).

The product of its (nonzero) digits is 2688, while the sum is 26.

The square root of 21206744 is about 4605.0780666564. The cubic root of 21206744 is about 276.7948452045.

Adding to 21206744 its reverse (44760212), we get a palindrome (65966956).

The spelling of 21206744 in words is "twenty-one million, two hundred six thousand, seven hundred forty-four".