21258717 has 4 divisors (see below), whose sum is σ = 28344960. Its totient is φ = 14172476.

The previous prime is 21258691. The next prime is 21258733. The reversal of 21258717 is 71785212.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21258717 - 2¹² = 21254621 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21258767) 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, 3543117 + ... + 3543122.

It is an arithmetic number, because the mean of its divisors is an integer number (7086240).

Almost surely, 2^21258717 is an apocalyptic number.

It is an amenable number.

21258717 is a deficient number, since it is larger than the sum of its proper divisors (7086243).

21258717 is an equidigital number, since it uses as much as digits as its factorization.

21258717 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7086242.

The product of its digits is 7840, while the sum is 33.

The square root of 21258717 is about 4610.7176231038. The cubic root of 21258717 is about 277.0207815433.

The spelling of 21258717 in words is "twenty-one million, two hundred fifty-eight thousand, seven hundred seventeen".