21087017 has 16 divisors (see below), whose sum is σ = 25497600. Its totient is φ = 17035920.

The previous prime is 21086981. The next prime is 21087019. The reversal of 21087017 is 71078012.

It is a cyclic number.

It is not a de Polignac number, because 21087017 - 2¹⁰ = 21085993 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21087019) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 43784 + ... + 44262.

It is an arithmetic number, because the mean of its divisors is an integer number (1593600).

Almost surely, 2^21087017 is an apocalyptic number.

It is an amenable number.

21087017 is a deficient number, since it is larger than the sum of its proper divisors (4410583).

21087017 is a wasteful number, since it uses less digits than its factorization.

21087017 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 836.

The product of its (nonzero) digits is 784, while the sum is 26.

The square root of 21087017 is about 4592.0602130199. The cubic root of 21087017 is about 276.2729612440.

The spelling of 21087017 in words is "twenty-one million, eighty-seven thousand, seventeen".