21385287 has 24 divisors (see below), whose sum is σ = 38513280. Its totient is φ = 11108880.

The previous prime is 21385283. The next prime is 21385307. The reversal of 21385287 is 78258312.

It is not a de Polignac number, because 21385287 - 2² = 21385283 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21385283) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 14737 + ... + 16122.

It is an arithmetic number, because the mean of its divisors is an integer number (1604720).

Almost surely, 2^21385287 is an apocalyptic number.

21385287 is a deficient number, since it is larger than the sum of its proper divisors (17127993).

21385287 is a wasteful number, since it uses less digits than its factorization.

21385287 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 30883 (or 30880 counting only the distinct ones).

The product of its digits is 26880, while the sum is 36.

The square root of 21385287 is about 4624.4228829120. The cubic root of 21385287 is about 277.5694688508.

The spelling of 21385287 in words is "twenty-one million, three hundred eighty-five thousand, two hundred eighty-seven".