21685550 has 48 divisors (see below), whose sum is σ = 42720480. Its totient is φ = 8173440.

The previous prime is 21685549. The next prime is 21685553. The reversal of 21685550 is 5558612.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21685553) by changing a digit.

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 23 ways as a sum of consecutive naturals, for example, 125264 + ... + 125436.

It is an arithmetic number, because the mean of its divisors is an integer number (890010).

Almost surely, 2^21685550 is an apocalyptic number.

21685550 is a deficient number, since it is larger than the sum of its proper divisors (21034930).

21685550 is a wasteful number, since it uses less digits than its factorization.

21685550 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 317 (or 312 counting only the distinct ones).

The product of its (nonzero) digits is 12000, while the sum is 32.

The square root of 21685550 is about 4656.7746348734. The cubic root of 21685550 is about 278.8625196773.

The spelling of 21685550 in words is "twenty-one million, six hundred eighty-five thousand, five hundred fifty".