21320812 has 12 divisors (see below), whose sum is σ = 39275320. Its totient is φ = 10099296.

The previous prime is 21320801. The next prime is 21320813. The reversal of 21320812 is 21802312.

It is a Harshad number since it is a multiple of its sum of digits (19).

It is a self number, because there is not a number n which added to its sum of digits gives 21320812.

It is not an unprimeable number, because it can be changed into a prime (21320813) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 140193 + ... + 140344.

Almost surely, 2^21320812 is an apocalyptic number.

It is an amenable number.

21320812 is a deficient number, since it is larger than the sum of its proper divisors (17954508).

21320812 is a wasteful number, since it uses less digits than its factorization.

21320812 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 280560 (or 280558 counting only the distinct ones).

The product of its (nonzero) digits is 192, while the sum is 19.

The square root of 21320812 is about 4617.4464804695. The cubic root of 21320812 is about 277.2902378231.

It can be divided in two parts, 213 and 20812, that added together give a square (21025 = 145²).

The spelling of 21320812 in words is "twenty-one million, three hundred twenty thousand, eight hundred twelve".