21755644 has 12 divisors (see below), whose sum is σ = 38215800. Its totient is φ = 10836848.

The previous prime is 21755633. The next prime is 21755651. The reversal of 21755644 is 44655712.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 9034 + ... + 11185.

It is an arithmetic number, because the mean of its divisors is an integer number (3184650).

Almost surely, 2^21755644 is an apocalyptic number.

It is an amenable number.

21755644 is a deficient number, since it is larger than the sum of its proper divisors (16460156).

21755644 is a wasteful number, since it uses less digits than its factorization.

21755644 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 20492 (or 20490 counting only the distinct ones).

The product of its digits is 33600, while the sum is 34.

The square root of 21755644 is about 4664.2945876091. The cubic root of 21755644 is about 279.1626514410.

The spelling of 21755644 in words is "twenty-one million, seven hundred fifty-five thousand, six hundred forty-four".