21840312 has 32 divisors (see below), whose sum is σ = 58801680. Its totient is φ = 6720000.

The previous prime is 21840283. The next prime is 21840319. The reversal of 21840312 is 21304812.

It is a Smith number, since the sum of its digits (21) coincides with the sum of the digits of its prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21840319) 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 7 ways as a sum of consecutive naturals, for example, 34689 + ... + 35312.

Almost surely, 2^21840312 is an apocalyptic number.

It is an amenable number.

21840312 is an abundant number, since it is smaller than the sum of its proper divisors (36961368).

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

21840312 is a wasteful number, since it uses less digits than its factorization.

21840312 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 70023 (or 70019 counting only the distinct ones).

The product of its (nonzero) digits is 384, while the sum is 21.

The square root of 21840312 is about 4673.3619590184. The cubic root of 21840312 is about 279.5243284283.

The spelling of 21840312 in words is "twenty-one million, eight hundred forty thousand, three hundred twelve".