21386840 has 16 divisors (see below), whose sum is σ = 48120480. Its totient is φ = 8554720.

The previous prime is 21386821. The next prime is 21386857. The reversal of 21386840 is 4868312.

It is a junction number, because it is equal to n+sod(n) for n = 21386797 and 21386806.

It is a congruent number.

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 3 ways as a sum of consecutive naturals, for example, 267296 + ... + 267375.

It is an arithmetic number, because the mean of its divisors is an integer number (3007530).

Almost surely, 2^21386840 is an apocalyptic number.

21386840 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21386840 is an abundant number, since it is smaller than the sum of its proper divisors (26733640).

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

21386840 is a wasteful number, since it uses less digits than its factorization.

21386840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 534682 (or 534678 counting only the distinct ones).

The product of its (nonzero) digits is 9216, while the sum is 32.

The square root of 21386840 is about 4624.5907927080. The cubic root of 21386840 is about 277.5761877218.

The spelling of 21386840 in words is "twenty-one million, three hundred eighty-six thousand, eight hundred forty".