21085638 has 16 divisors (see below), whose sum is σ = 48195840. Its totient is φ = 6024456.

The previous prime is 21085621. The next prime is 21085643. The reversal of 21085638 is 83658012.

It is a happy number.

It is a junction number, because it is equal to n+sod(n) for n = 21085599 and 21085608.

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, 250978 + ... + 251061.

It is an arithmetic number, because the mean of its divisors is an integer number (3012240).

Almost surely, 2^21085638 is an apocalyptic number.

21085638 is an abundant number, since it is smaller than the sum of its proper divisors (27110202).

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

21085638 is a wasteful number, since it uses less digits than its factorization.

21085638 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 502051.

The product of its (nonzero) digits is 11520, while the sum is 33.

The square root of 21085638 is about 4591.9100600948. The cubic root of 21085638 is about 276.2669387592.

The spelling of 21085638 in words is "twenty-one million, eighty-five thousand, six hundred thirty-eight".