21104557 has 4 divisors (see below), whose sum is σ = 21114016. Its totient is φ = 21095100.

The previous prime is 21104549. The next prime is 21104561. The reversal of 21104557 is 75540112.

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 21104557 - 2³ = 21104549 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 (21104507) 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, 682 + ... + 6532.

It is an arithmetic number, because the mean of its divisors is an integer number (5278504).

Almost surely, 2^21104557 is an apocalyptic number.

It is an amenable number.

21104557 is a deficient number, since it is larger than the sum of its proper divisors (9459).

21104557 is an equidigital number, since it uses as much as digits as its factorization.

21104557 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9458.

The product of its (nonzero) digits is 1400, while the sum is 25.

The square root of 21104557 is about 4593.9696342053. The cubic root of 21104557 is about 276.3495405090.

Adding to 21104557 its reverse (75540112), we get a palindrome (96644669).

The spelling of 21104557 in words is "twenty-one million, one hundred four thousand, five hundred fifty-seven".