21085487 has 4 divisors (see below), whose sum is σ = 21765696. Its totient is φ = 20405280.

The previous prime is 21085453. The next prime is 21085511. The reversal of 21085487 is 78458012.

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

It is a cyclic number.

It is not a de Polignac number, because 21085487 - 2¹⁰ = 21084463 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21085087) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 340058 + ... + 340119.

It is an arithmetic number, because the mean of its divisors is an integer number (5441424).

Almost surely, 2^21085487 is an apocalyptic number.

21085487 is a deficient number, since it is larger than the sum of its proper divisors (680209).

21085487 is an equidigital number, since it uses as much as digits as its factorization.

21085487 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 680208.

The product of its (nonzero) digits is 17920, while the sum is 35.

The square root of 21085487 is about 4591.8936181057. The cubic root of 21085487 is about 276.2662792833.

The spelling of 21085487 in words is "twenty-one million, eighty-five thousand, four hundred eighty-seven".