21216330 has 48 divisors (see below), whose sum is σ = 57212064. Its totient is φ = 5657040.

The previous prime is 21216263. The next prime is 21216361. The reversal of 21216330 is 3361212.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 1936 + ... + 6795.

It is an arithmetic number, because the mean of its divisors is an integer number (1191918).

Almost surely, 2^21216330 is an apocalyptic number.

21216330 is an abundant number, since it is smaller than the sum of its proper divisors (35995734).

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

21216330 is an equidigital number, since it uses as much as digits as its factorization.

21216330 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8753 (or 8741 counting only the distinct ones).

The product of its (nonzero) digits is 216, while the sum is 18.

The square root of 21216330 is about 4606.1187566106. The cubic root of 21216330 is about 276.8365450791.

Adding to 21216330 its reverse (3361212), we get a palindrome (24577542).

The spelling of 21216330 in words is "twenty-one million, two hundred sixteen thousand, three hundred thirty".