21085646 has 4 divisors (see below), whose sum is σ = 31628472. Its totient is φ = 10542822.

The previous prime is 21085643. The next prime is 21085703. The reversal of 21085646 is 64658012.

It is a semiprime because it is the product of two primes.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21085643) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5271410 + ... + 5271413.

It is an arithmetic number, because the mean of its divisors is an integer number (7907118).

Almost surely, 2^21085646 is an apocalyptic number.

21085646 is a deficient number, since it is larger than the sum of its proper divisors (10542826).

21085646 is a wasteful number, since it uses less digits than its factorization.

21085646 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10542825.

The product of its (nonzero) digits is 11520, while the sum is 32.

The square root of 21085646 is about 4591.9109311919. The cubic root of 21085646 is about 276.2669736982.

The spelling of 21085646 in words is "twenty-one million, eighty-five thousand, six hundred forty-six".