21147644 has 12 divisors (see below), whose sum is σ = 42295344. Its totient is φ = 9063264.

The previous prime is 21147617. The next prime is 21147647. The reversal of 21147644 is 44674112.

It is a happy number.

21147644 is an admirable number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21147647) 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, 377609 + ... + 377664.

It is an arithmetic number, because the mean of its divisors is an integer number (3524612).

Almost surely, 2^21147644 is an apocalyptic number.

It is an amenable number.

21147644 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.

21147644 is a wasteful number, since it uses less digits than its factorization.

21147644 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 755284 (or 755282 counting only the distinct ones).

The product of its digits is 5376, while the sum is 29.

The square root of 21147644 is about 4598.6567604030. The cubic root of 21147644 is about 276.5374774663.

The spelling of 21147644 in words is "twenty-one million, one hundred forty-seven thousand, six hundred forty-four".