21685340 has 12 divisors (see below), whose sum is σ = 45539256. Its totient is φ = 8674128.

The previous prime is 21685333. The next prime is 21685361. The reversal of 21685340 is 4358612.

It is a congruent number.

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, 542114 + ... + 542153.

It is an arithmetic number, because the mean of its divisors is an integer number (3794938).

Almost surely, 2^21685340 is an apocalyptic number.

21685340 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21685340 is an abundant number, since it is smaller than the sum of its proper divisors (23853916).

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

21685340 is a wasteful number, since it uses less digits than its factorization.

21685340 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1084276 (or 1084274 counting only the distinct ones).

The product of its (nonzero) digits is 5760, while the sum is 29.

The square root of 21685340 is about 4656.7520870237. The cubic root of 21685340 is about 278.8616195184.

The spelling of 21685340 in words is "twenty-one million, six hundred eighty-five thousand, three hundred forty".