21355640 has 32 divisors (see below), whose sum is σ = 48870000. Its totient is φ = 8396544.

The previous prime is 21355637. The next prime is 21355657. The reversal of 21355640 is 4655312.

It is a congruent number.

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, 2165 + ... + 6884.

Almost surely, 2^21355640 is an apocalyptic number.

21355640 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21355640 is an abundant number, since it is smaller than the sum of its proper divisors (27514360).

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

21355640 is a wasteful number, since it uses less digits than its factorization.

21355640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9119 (or 9115 counting only the distinct ones).

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

The square root of 21355640 is about 4621.2162901124. The cubic root of 21355640 is about 277.4411421853.

The spelling of 21355640 in words is "twenty-one million, three hundred fifty-five thousand, six hundred forty".