21221748 has 18 divisors (see below), whose sum is σ = 53643954. Its totient is φ = 7073904.

The previous prime is 21221743. The next prime is 21221749. The reversal of 21221748 is 84712212.

It can be written as a sum of positive squares in only one way, i.e., 17489124 + 3732624 = 4182^2 + 1932^2 .

It is a tau number, because it is divible by the number of its divisors (18).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21221741) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 294711 + ... + 294782.

Almost surely, 2^21221748 is an apocalyptic number.

It is an amenable number.

21221748 is an abundant number, since it is smaller than the sum of its proper divisors (32422206).

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

21221748 is a wasteful number, since it uses less digits than its factorization.

21221748 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 589503 (or 589498 counting only the distinct ones).

The product of its digits is 1792, while the sum is 27.

The square root of 21221748 is about 4606.7068498006. The cubic root of 21221748 is about 276.8601082612.

The spelling of 21221748 in words is "twenty-one million, two hundred twenty-one thousand, seven hundred forty-eight".