21800644 has 6 divisors (see below), whose sum is σ = 38151134. Its totient is φ = 10900320.

The previous prime is 21800641. The next prime is 21800651. The reversal of 21800644 is 44600812.

It can be written as a sum of positive squares in only one way, i.e., 11303044 + 10497600 = 3362^2 + 3240^2 .

It is not an unprimeable number, because it can be changed into a prime (21800641) 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, 2725077 + ... + 2725084.

Almost surely, 2^21800644 is an apocalyptic number.

It is an amenable number.

21800644 is a deficient number, since it is larger than the sum of its proper divisors (16350490).

21800644 is a wasteful number, since it uses less digits than its factorization.

21800644 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5450165 (or 5450163 counting only the distinct ones).

The product of its (nonzero) digits is 1536, while the sum is 25.

The square root of 21800644 is about 4669.1159762850. The cubic root of 21800644 is about 279.3549949057.

The spelling of 21800644 in words is "twenty-one million, eight hundred thousand, six hundred forty-four".