21655340 has 24 divisors (see below), whose sum is σ = 51973152. Its totient is φ = 7424640.

The previous prime is 21655327. The next prime is 21655367. The reversal of 21655340 is 4355612.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 77201 + ... + 77480.

It is an arithmetic number, because the mean of its divisors is an integer number (2165548).

Almost surely, 2^21655340 is an apocalyptic number.

21655340 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21655340 is an abundant number, since it is smaller than the sum of its proper divisors (30317812).

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

21655340 is a wasteful number, since it uses less digits than its factorization.

21655340 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 154697 (or 154695 counting only the distinct ones).

The product of its (nonzero) digits is 3600, while the sum is 26.

The square root of 21655340 is about 4653.5298430331. The cubic root of 21655340 is about 278.7329656385.

The spelling of 21655340 in words is "twenty-one million, six hundred fifty-five thousand, three hundred forty".