21306372 has 96 divisors (see below), whose sum is σ = 58060800. Its totient is φ = 6031872.

The previous prime is 21306359. The next prime is 21306407. The reversal of 21306372 is 27360312.

It is a super-2 number, since 2×21306372² = 907922975604768, which contains 22 as substring.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 89029 + ... + 89267.

It is an arithmetic number, because the mean of its divisors is an integer number (604800).

Almost surely, 2^21306372 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21306372, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29030400).

21306372 is an abundant number, since it is smaller than the sum of its proper divisors (36754428).

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

21306372 is a wasteful number, since it uses less digits than its factorization.

21306372 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 305 (or 303 counting only the distinct ones).

The product of its (nonzero) digits is 1512, while the sum is 24.

The square root of 21306372 is about 4615.8825808289. The cubic root of 21306372 is about 277.2276233328.

Adding to 21306372 its reverse (27360312), we get a palindrome (48666684).

The spelling of 21306372 in words is "twenty-one million, three hundred six thousand, three hundred seventy-two".