21113557 has 4 divisors (see below), whose sum is σ = 21511980. Its totient is φ = 20715136.

The previous prime is 21113549. The next prime is 21113581. The reversal of 21113557 is 75531112.

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 17631601 + 3481956 = 4199^2 + 1866^2 .

It is a cyclic number.

It is not a de Polignac number, because 21113557 - 2³ = 21113549 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 (21113527) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 199132 + ... + 199237.

It is an arithmetic number, because the mean of its divisors is an integer number (5377995).

Almost surely, 2^21113557 is an apocalyptic number.

It is an amenable number.

21113557 is a deficient number, since it is larger than the sum of its proper divisors (398423).

21113557 is an equidigital number, since it uses as much as digits as its factorization.

21113557 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 398422.

The product of its digits is 1050, while the sum is 25.

The square root of 21113557 is about 4594.9490747994. The cubic root of 21113557 is about 276.3888178461.

Adding to 21113557 its reverse (75531112), we get a palindrome (96644669).

The spelling of 21113557 in words is "twenty-one million, one hundred thirteen thousand, five hundred fifty-seven".