21455717 has 4 divisors (see below), whose sum is σ = 22717836. Its totient is φ = 20193600.

The previous prime is 21455701. The next prime is 21455719. The reversal of 21455717 is 71755412.

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

It can be written as a sum of positive squares in 2 ways, for example, as 12208036 + 9247681 = 3494^2 + 3041^2 .

It is a cyclic number.

It is not a de Polignac number, because 21455717 - 2⁴ = 21455701 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 (21455719) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 631034 + ... + 631067.

It is an arithmetic number, because the mean of its divisors is an integer number (5679459).

Almost surely, 2^21455717 is an apocalyptic number.

It is an amenable number.

21455717 is a deficient number, since it is larger than the sum of its proper divisors (1262119).

21455717 is a wasteful number, since it uses less digits than its factorization.

21455717 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1262118.

The product of its digits is 9800, while the sum is 32.

The square root of 21455717 is about 4632.0316276986. The cubic root of 21455717 is about 277.8738493942.

The spelling of 21455717 in words is "twenty-one million, four hundred fifty-five thousand, seven hundred seventeen".