21383840 has 24 divisors (see below), whose sum is σ = 50519700. Its totient is φ = 8553472.

The previous prime is 21383839. The next prime is 21383863. The reversal of 21383840 is 4838312.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 17205904 + 4177936 = 4148^2 + 2044^2 .

It is a super-2 number, since 2×21383840² = 914537226291200, which contains 22 as substring.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 66665 + ... + 66984.

Almost surely, 2^21383840 is an apocalyptic number.

21383840 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21383840 is an abundant number, since it is smaller than the sum of its proper divisors (29135860).

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

21383840 is a wasteful number, since it uses less digits than its factorization.

21383840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 133664 (or 133656 counting only the distinct ones).

The product of its (nonzero) digits is 4608, while the sum is 29.

The square root of 21383840 is about 4624.2664283105. The cubic root of 21383840 is about 277.5632082836.

The spelling of 21383840 in words is "twenty-one million, three hundred eighty-three thousand, eight hundred forty".