21068557 has 4 divisors (see below), whose sum is σ = 21077856. Its totient is φ = 21059260.

The previous prime is 21068543. The next prime is 21068563. The reversal of 21068557 is 75586012.

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, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 21068557 - 2¹¹ = 21066509 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 (21068527) 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, 1218 + ... + 6604.

It is an arithmetic number, because the mean of its divisors is an integer number (5269464).

Almost surely, 2^21068557 is an apocalyptic number.

It is an amenable number.

21068557 is a deficient number, since it is larger than the sum of its proper divisors (9299).

21068557 is an equidigital number, since it uses as much as digits as its factorization.

21068557 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9298.

The product of its (nonzero) digits is 16800, while the sum is 34.

The square root of 21068557 is about 4590.0497818651. The cubic root of 21068557 is about 276.1923194001.

The spelling of 21068557 in words is "twenty-one million, sixty-eight thousand, five hundred fifty-seven".