21316812 has 72 divisors (see below), whose sum is σ = 55904688. Its totient is φ = 6314880.

The previous prime is 21316783. The next prime is 21316819. The reversal of 21316812 is 21861312.

It is not an unprimeable number, because it can be changed into a prime (21316819) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 76818 + ... + 77094.

It is an arithmetic number, because the mean of its divisors is an integer number (776454).

Almost surely, 2^21316812 is an apocalyptic number.

21316812 is a gapful number since it is divisible by the number (22) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21316812, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27952344).

21316812 is an abundant number, since it is smaller than the sum of its proper divisors (34587876).

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

21316812 is a wasteful number, since it uses less digits than its factorization.

21316812 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 359 (or 346 counting only the distinct ones).

The product of its digits is 576, while the sum is 24.

The square root of 21316812 is about 4617.0133203187. The cubic root of 21316812 is about 277.2728959207.

The spelling of 21316812 in words is "twenty-one million, three hundred sixteen thousand, eight hundred twelve".