21216648 has 32 divisors (see below), whose sum is σ = 54754560. Its totient is φ = 6843840.

The previous prime is 21216631. The next prime is 21216659. The reversal of 21216648 is 84661212.

It is a nude number because it is divisible by every one of its digits.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 13515 + ... + 15002.

It is an arithmetic number, because the mean of its divisors is an integer number (1711080).

Almost surely, 2^21216648 is an apocalyptic number.

It is an amenable number.

21216648 is an abundant number, since it is smaller than the sum of its proper divisors (33537912).

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

21216648 is a wasteful number, since it uses less digits than its factorization.

21216648 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 28557 (or 28553 counting only the distinct ones).

The product of its digits is 4608, while the sum is 30.

The square root of 21216648 is about 4606.1532757823. The cubic root of 21216648 is about 276.8379281895.

The spelling of 21216648 in words is "twenty-one million, two hundred sixteen thousand, six hundred forty-eight".