21806340 has 24 divisors (see below), whose sum is σ = 61057920. Its totient is φ = 5815008.

The previous prime is 21806333. The next prime is 21806353. The reversal of 21806340 is 4360812.

It is a happy number.

It is a self number, because there is not a number n which added to its sum of digits gives 21806340.

It is an unprimeable number.

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, 181660 + ... + 181779.

It is an arithmetic number, because the mean of its divisors is an integer number (2544080).

Almost surely, 2^21806340 is an apocalyptic number.

21806340 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21806340 is an abundant number, since it is smaller than the sum of its proper divisors (39251580).

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

21806340 is a wasteful number, since it uses less digits than its factorization.

21806340 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 363451 (or 363449 counting only the distinct ones).

The product of its (nonzero) digits is 1152, while the sum is 24.

The square root of 21806340 is about 4669.7259020204. The cubic root of 21806340 is about 279.3793224361.

The spelling of 21806340 in words is "twenty-one million, eight hundred six thousand, three hundred forty".