21168557 has 4 divisors (see below), whose sum is σ = 21181020. Its totient is φ = 21156096.

The previous prime is 21168547. The next prime is 21168577. The reversal of 21168557 is 75586112.

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 18498601 + 2669956 = 4301^2 + 1634^2 .

It is a cyclic number.

It is not a de Polignac number, because 21168557 - 2⁴ = 21168541 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 (21168517) 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, 3188 + ... + 7245.

It is an arithmetic number, because the mean of its divisors is an integer number (5295255).

Almost surely, 2^21168557 is an apocalyptic number.

It is an amenable number.

21168557 is a deficient number, since it is larger than the sum of its proper divisors (12463).

21168557 is a wasteful number, since it uses less digits than its factorization.

21168557 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12462.

The product of its digits is 16800, while the sum is 35.

The square root of 21168557 is about 4600.9300146818. The cubic root of 21168557 is about 276.6286038184.

The spelling of 21168557 in words is "twenty-one million, one hundred sixty-eight thousand, five hundred fifty-seven".